* [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID @ 2019-08-11 20:33 Adrian Reber 2019-08-11 20:33 ` [PATCH v5 2/2] selftests: add tests for clone3() Adrian Reber ` (2 more replies) 0 siblings, 3 replies; 8+ messages in thread From: Adrian Reber @ 2019-08-11 20:33 UTC (permalink / raw) To: Christian Brauner, Eric Biederman, Pavel Emelianov, Jann Horn, Oleg Nesterov, Dmitry Safonov Cc: linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov, Adrian Reber The main motivation to add set_tid to clone3() is CRIU. To restore a process with the same PID/TID CRIU currently uses /proc/sys/kernel/ns_last_pid. It writes the desired (PID - 1) to ns_last_pid and then (quickly) does a clone(). This works most of the time, but it is racy. It is also slow as it requires multiple syscalls. Extending clone3() to support set_tid makes it possible restore a process using CRIU without accessing /proc/sys/kernel/ns_last_pid and race free (as long as the desired PID/TID is available). This clone3() extension places the same restrictions (CAP_SYS_ADMIN) on clone3() with set_tid as they are currently in place for ns_last_pid. Signed-off-by: Adrian Reber <areber@redhat.com> --- v2: - Removed (size < sizeof(struct clone_args)) as discussed with Christian and Dmitry - Added comment to ((set_tid != 1) && idr_get_cursor() <= 1) (Oleg) - Use idr_alloc() instead of idr_alloc_cyclic() (Oleg) v3: - Return EEXIST if PID is already in use (Christian) - Drop CLONE_SET_TID (Christian and Oleg) - Use idr_is_empty() instead of idr_get_cursor() (Oleg) - Handle different `struct clone_args` sizes (Dmitry) v4: - Rework struct size check with defines (Christian) - Reduce number of set_tid checks (Oleg) - Less parentheses and more robust code (Oleg) - Do ns_capable() on correct user_ns (Oleg, Christian) v5: - make set_tid checks earlier in alloc_pid() (Christian) - remove unnecessary comment and struct size check (Christian) --- include/linux/pid.h | 2 +- include/linux/sched/task.h | 1 + include/uapi/linux/sched.h | 1 + kernel/fork.c | 22 ++++++++++++++++++++-- kernel/pid.c | 36 +++++++++++++++++++++++++++++------- 5 files changed, 52 insertions(+), 10 deletions(-) diff --git a/include/linux/pid.h b/include/linux/pid.h index 2a83e434db9d..052000db0ced 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -116,7 +116,7 @@ extern struct pid *find_vpid(int nr); extern struct pid *find_get_pid(int nr); extern struct pid *find_ge_pid(int nr, struct pid_namespace *); -extern struct pid *alloc_pid(struct pid_namespace *ns); +extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t set_tid); extern void free_pid(struct pid *pid); extern void disable_pid_allocation(struct pid_namespace *ns); diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 0497091e40c1..4f2a80564332 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -26,6 +26,7 @@ struct kernel_clone_args { unsigned long stack; unsigned long stack_size; unsigned long tls; + pid_t set_tid; }; /* diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index b3105ac1381a..e1ce103a2c47 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -45,6 +45,7 @@ struct clone_args { __aligned_u64 stack; __aligned_u64 stack_size; __aligned_u64 tls; + __aligned_u64 set_tid; }; /* diff --git a/kernel/fork.c b/kernel/fork.c index 2852d0e76ea3..0365041243b1 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -117,6 +117,13 @@ */ #define MAX_THREADS FUTEX_TID_MASK +/* + * Different sizes of struct clone_args + */ +#define CLONE3_ARGS_SIZE_V0 64 +/* V1 includes set_tid */ +#define CLONE3_ARGS_SIZE_V1 72 + /* * Protected counters by write_lock_irq(&tasklist_lock) */ @@ -2031,7 +2038,13 @@ static __latent_entropy struct task_struct *copy_process( stackleak_task_init(p); if (pid != &init_struct_pid) { - pid = alloc_pid(p->nsproxy->pid_ns_for_children); + if (args->set_tid && !ns_capable( + p->nsproxy->pid_ns_for_children->user_ns, + CAP_SYS_ADMIN)) { + retval = -EPERM; + goto bad_fork_cleanup_thread; + } + pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid); if (IS_ERR(pid)) { retval = PTR_ERR(pid); goto bad_fork_cleanup_thread; @@ -2535,9 +2548,13 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, if (unlikely(size > PAGE_SIZE)) return -E2BIG; - if (unlikely(size < sizeof(struct clone_args))) + if (unlikely(size < CLONE3_ARGS_SIZE_V0)) return -EINVAL; + if (size < sizeof(struct clone_args)) + memset((void *)&args + size, 0, + sizeof(struct clone_args) - size); + if (unlikely(!access_ok(uargs, size))) return -EFAULT; @@ -2571,6 +2588,7 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, .stack = args.stack, .stack_size = args.stack_size, .tls = args.tls, + .set_tid = args.set_tid, }; return 0; diff --git a/kernel/pid.c b/kernel/pid.c index 0a9f2e437217..c3ce82f8206b 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -157,7 +157,7 @@ void free_pid(struct pid *pid) call_rcu(&pid->rcu, delayed_put_pid); } -struct pid *alloc_pid(struct pid_namespace *ns) +struct pid *alloc_pid(struct pid_namespace *ns, int set_tid) { struct pid *pid; enum pid_type type; @@ -166,6 +166,9 @@ struct pid *alloc_pid(struct pid_namespace *ns) struct upid *upid; int retval = -ENOMEM; + if (set_tid < 0 || set_tid >= pid_max) + return ERR_PTR(-EINVAL); + pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); if (!pid) return ERR_PTR(retval); @@ -186,12 +189,31 @@ struct pid *alloc_pid(struct pid_namespace *ns) if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS) pid_min = RESERVED_PIDS; - /* - * Store a null pointer so find_pid_ns does not find - * a partially initialized PID (see below). - */ - nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min, - pid_max, GFP_ATOMIC); + if (set_tid) { + /* + * Also fail if a PID != 1 is requested + * and no PID 1 exists. + */ + nr = -EINVAL; + if (set_tid == 1 || !idr_is_empty(&tmp->idr)) + nr = idr_alloc(&tmp->idr, NULL, set_tid, + set_tid + 1, GFP_ATOMIC); + /* + * If ENOSPC is returned it means that the PID is + * alreay in use. Return EEXIST in that case. + */ + if (nr == -ENOSPC) + nr = -EEXIST; + /* Only use set_tid for one PID namespace. */ + set_tid = 0; + } else { + /* + * Store a null pointer so find_pid_ns does not find + * a partially initialized PID (see below). + */ + nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min, + pid_max, GFP_ATOMIC); + } spin_unlock_irq(&pidmap_lock); idr_preload_end(); -- 2.21.0 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v5 2/2] selftests: add tests for clone3() 2019-08-11 20:33 [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Adrian Reber @ 2019-08-11 20:33 ` Adrian Reber 2019-08-11 21:37 ` Christian Brauner 2019-08-12 9:40 ` [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Christian Brauner 2019-08-12 16:37 ` Oleg Nesterov 2 siblings, 1 reply; 8+ messages in thread From: Adrian Reber @ 2019-08-11 20:33 UTC (permalink / raw) To: Christian Brauner, Eric Biederman, Pavel Emelianov, Jann Horn, Oleg Nesterov, Dmitry Safonov Cc: linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov, Adrian Reber This tests clone3() with and without set_tid to see if all desired PIDs are working as expected. The test tries to clone3() with a set_tid of -1, 1, pid_max, a PID which is already in use and an unused PID. The same tests are also running in PID namespace. Signed-off-by: Adrian Reber <areber@redhat.com> --- tools/testing/selftests/clone3/.gitignore | 2 + tools/testing/selftests/clone3/Makefile | 11 ++ tools/testing/selftests/clone3/clone3.c | 141 +++++++++++++++ .../testing/selftests/clone3/clone3_set_tid.c | 161 ++++++++++++++++++ 4 files changed, 315 insertions(+) create mode 100644 tools/testing/selftests/clone3/.gitignore create mode 100644 tools/testing/selftests/clone3/Makefile create mode 100644 tools/testing/selftests/clone3/clone3.c create mode 100644 tools/testing/selftests/clone3/clone3_set_tid.c diff --git a/tools/testing/selftests/clone3/.gitignore b/tools/testing/selftests/clone3/.gitignore new file mode 100644 index 000000000000..c63c64a78ddf --- /dev/null +++ b/tools/testing/selftests/clone3/.gitignore @@ -0,0 +1,2 @@ +clone3_set_tid +clone3 diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile new file mode 100644 index 000000000000..4efcf45b995b --- /dev/null +++ b/tools/testing/selftests/clone3/Makefile @@ -0,0 +1,11 @@ +# SPDX-License-Identifier: GPL-2.0 +uname_M := $(shell uname -m 2>/dev/null || echo not) +ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/) + +CFLAGS += -I../../../../usr/include/ + +ifeq ($(ARCH),x86_64) + TEST_GEN_PROGS := clone3 clone3_set_tid +endif + +include ../lib.mk diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c new file mode 100644 index 000000000000..55a6915566b8 --- /dev/null +++ b/tools/testing/selftests/clone3/clone3.c @@ -0,0 +1,141 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* Based on Christian Brauner's clone3() example */ + +#define _GNU_SOURCE +#include <errno.h> +#include <linux/types.h> +#include <linux/sched.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/syscall.h> +#include <sys/types.h> +#include <sys/un.h> +#include <sys/wait.h> +#include <unistd.h> +#include <sched.h> + +#include "../kselftest.h" + +static pid_t raw_clone(struct clone_args *args) +{ + return syscall(__NR_clone3, args, sizeof(struct clone_args)); +} + +static int call_clone3(int flags) +{ + struct clone_args args = {0}; + pid_t ppid = -1; + pid_t pid = -1; + int status; + + args.flags = flags; + args.exit_signal = SIGCHLD; + + pid = raw_clone(&args); + if (pid < 0) { + ksft_print_msg("%s - Failed to create new process\n", + strerror(errno)); + return -errno; + } + + if (pid == 0) { + ksft_print_msg("I am the child, my PID is %d\n", getpid()); + _exit(EXIT_SUCCESS); + } + + ppid = getpid(); + ksft_print_msg("I am the parent (%d). My child's pid is %d\n", + ppid, pid); + + (void)wait(&status); + if (WEXITSTATUS(status)) + return WEXITSTATUS(status); + + return 0; +} + +static int test_clone3(int flags, int expected) +{ + int ret; + + ksft_print_msg("[%d] Trying clone3() with flags 0x%x\n", + getpid(), flags); + ret = call_clone3(flags); + ksft_print_msg("[%d] clone3() with flags says :%d expected %d\n", + getpid(), ret, expected); + if (ret != expected) + ksft_exit_fail_msg( + "[%d] Result (%d) is different than expected (%d)\n", + getpid(), ret, expected); + ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n", + getpid(), ret, expected); + return 0; +} +int main(int argc, char *argv[]) +{ + int ret = -1; + pid_t pid; + + ksft_print_header(); + ksft_set_plan(3); + + /* Just a simple clone3() should return 0.*/ + if (test_clone3(0, 0)) + goto on_error; + /* Do a clone3() in a new PID NS.*/ + if (test_clone3(CLONE_NEWPID, 0)) + goto on_error; + ksft_print_msg("First unshare\n"); + if (unshare(CLONE_NEWPID)) + goto on_error; + /* + * Before clone3()ing in a new PID NS with + * CLONE_NEWPID a fork() is necessary. + */ + if (test_clone3(CLONE_NEWPID, -EINVAL)) + goto on_error; + pid = fork(); + if (pid < 0) { + ksft_print_msg("First fork() failed\n"); + goto on_error; + } + if (pid > 0) { + (void)wait(NULL); + goto parent_out; + } + ksft_set_plan(6); + if (test_clone3(CLONE_NEWPID, 0)) + goto on_error; + if (test_clone3(0, 0)) + goto on_error; + ksft_print_msg("Second unshare\n"); + if (unshare(CLONE_NEWPID)) + goto on_error; + /* + * Before clone3()ing in a new PID NS with + * CLONE_NEWPID a fork() is necessary. + */ + if (test_clone3(CLONE_NEWPID, -EINVAL)) + goto on_error; + pid = fork(); + if (pid < 0) { + ksft_print_msg("Second fork() failed\n"); + goto on_error; + } + if (pid > 0) { + (void)wait(NULL); + goto parent_out; + } + ksft_set_plan(8); + if (test_clone3(CLONE_NEWPID, 0)) + goto on_error; + if (test_clone3(0, 0)) + goto on_error; + +parent_out: + ret = 0; +on_error: + + return !ret ? ksft_exit_pass() : ksft_exit_fail(); +} diff --git a/tools/testing/selftests/clone3/clone3_set_tid.c b/tools/testing/selftests/clone3/clone3_set_tid.c new file mode 100644 index 000000000000..f5012e84dcb3 --- /dev/null +++ b/tools/testing/selftests/clone3/clone3_set_tid.c @@ -0,0 +1,161 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* Based on Christian Brauner's clone3() example */ + +#define _GNU_SOURCE +#include <errno.h> +#include <linux/types.h> +#include <linux/sched.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/syscall.h> +#include <sys/types.h> +#include <sys/un.h> +#include <sys/wait.h> +#include <unistd.h> +#include <sched.h> + +#include "../kselftest.h" + +static pid_t raw_clone(struct clone_args *args) +{ + return syscall(__NR_clone3, args, sizeof(struct clone_args)); +} + +static int call_clone3_set_tid(int set_tid, int flags) +{ + struct clone_args args = {0}; + pid_t ppid = -1; + pid_t pid = -1; + int status; + + args.flags = flags; + args.exit_signal = SIGCHLD; + args.set_tid = set_tid; + + pid = raw_clone(&args); + if (pid < 0) { + ksft_print_msg("%s - Failed to create new process\n", + strerror(errno)); + return -errno; + } + + if (pid == 0) { + ksft_print_msg("I am the child, my PID is %d (expected %d)\n", + getpid(), set_tid); + if (set_tid != getpid()) + _exit(EXIT_FAILURE); + _exit(EXIT_SUCCESS); + } + + ppid = getpid(); + ksft_print_msg("I am the parent (%d). My child's pid is %d\n", + ppid, pid); + + (void)wait(&status); + if (WEXITSTATUS(status)) + return WEXITSTATUS(status); + + return 0; +} + +static int test_clone3_set_tid(int set_tid, int flags, int expected) +{ + int ret; + + ksft_print_msg( + "[%d] Trying clone3() with CLONE_SET_TID to %d and 0x%x\n", + getpid(), set_tid, flags); + ret = call_clone3_set_tid(set_tid, flags); + ksft_print_msg( + "[%d] clone3() with CLONE_SET_TID %d says :%d - expected %d\n", + getpid(), set_tid, ret, expected); + if (ret != expected) + ksft_exit_fail_msg( + "[%d] Result (%d) is different than expected (%d)\n", + getpid(), ret, expected); + ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n", + getpid(), ret, expected); + return 0; +} +int main(int argc, char *argv[]) +{ + FILE *f; + int pid_max = 0; + pid_t pid; + pid_t ns_pid; + int ret = -1; + + ksft_print_header(); + ksft_set_plan(13); + + f = fopen("/proc/sys/kernel/pid_max", "r"); + if (f == NULL) + ksft_exit_fail_msg( + "%s - Could not open /proc/sys/kernel/pid_max\n", + strerror(errno)); + fscanf(f, "%d", &pid_max); + fclose(f); + ksft_print_msg("/proc/sys/kernel/pid_max %d\n", pid_max); + + /* First try with an invalid PID */ + if (test_clone3_set_tid(-1, 0, -EINVAL)) + goto on_error; + if (test_clone3_set_tid(-1, CLONE_NEWPID, -EINVAL)) + goto on_error; + /* Then with PID 1 */ + if (test_clone3_set_tid(1, 0, -EEXIST)) + goto on_error; + /* PID 1 should not fail in a PID namespace */ + if (test_clone3_set_tid(1, CLONE_NEWPID, 0)) + goto on_error; + /* pid_max should fail everywhere */ + if (test_clone3_set_tid(pid_max, 0, -EINVAL)) + goto on_error; + if (test_clone3_set_tid(pid_max, CLONE_NEWPID, -EINVAL)) + goto on_error; + /* Find the current active PID */ + pid = fork(); + if (pid == 0) { + ksft_print_msg("Child has PID %d\n", getpid()); + sleep(1); + _exit(EXIT_SUCCESS); + } + /* Try to create a process with that PID should fail */ + if (test_clone3_set_tid(pid, 0, -EEXIST)) + goto on_error; + (void)wait(NULL); + /* After the child has finished, try again with the same PID */ + if (test_clone3_set_tid(pid, 0, 0)) + goto on_error; + /* This should fail as there is no PID 1 in that namespace */ + if (test_clone3_set_tid(pid, CLONE_NEWPID, -EINVAL)) + goto on_error; + unshare(CLONE_NEWPID); + if (test_clone3_set_tid(10, 0, -EINVAL)) + goto on_error; + /* Let's create a PID 1 */ + ns_pid = fork(); + if (ns_pid == 0) { + ksft_print_msg("Child in PID namespace has PID %d\n", getpid()); + sleep(1); + _exit(EXIT_SUCCESS); + } + /* + * Now, after the unshare() it should be possible to create a process + * with another ID than 1 in the PID namespace. + */ + if (test_clone3_set_tid(2, 0, 0)) + goto on_error; + /* Use a different PID in this namespace. */ + if (test_clone3_set_tid(2222, 0, 0)) + goto on_error; + if (test_clone3_set_tid(1, 0, -EEXIST)) + goto on_error; + (void)wait(NULL); + + ret = 0; +on_error: + + return !ret ? ksft_exit_pass() : ksft_exit_fail(); +} -- 2.21.0 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v5 2/2] selftests: add tests for clone3() 2019-08-11 20:33 ` [PATCH v5 2/2] selftests: add tests for clone3() Adrian Reber @ 2019-08-11 21:37 ` Christian Brauner 0 siblings, 0 replies; 8+ messages in thread From: Christian Brauner @ 2019-08-11 21:37 UTC (permalink / raw) To: Adrian Reber, Eric Biederman, Pavel Emelianov, Jann Horn, Oleg Nesterov, Dmitry Safonov Cc: linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov On August 11, 2019 1:33:27 PM PDT, Adrian Reber <areber@redhat.com> wrote: >This tests clone3() with and without set_tid to see if all desired PIDs >are working as expected. The test tries to clone3() with a set_tid of >-1, 1, pid_max, a PID which is already in use and an unused PID. The >same tests are also running in PID namespace. > >Signed-off-by: Adrian Reber <areber@redhat.com> >--- > tools/testing/selftests/clone3/.gitignore | 2 + > tools/testing/selftests/clone3/Makefile | 11 ++ > tools/testing/selftests/clone3/clone3.c | 141 +++++++++++++++ > .../testing/selftests/clone3/clone3_set_tid.c | 161 ++++++++++++++++++ > 4 files changed, 315 insertions(+) > create mode 100644 tools/testing/selftests/clone3/.gitignore > create mode 100644 tools/testing/selftests/clone3/Makefile > create mode 100644 tools/testing/selftests/clone3/clone3.c > create mode 100644 tools/testing/selftests/clone3/clone3_set_tid.c > >diff --git a/tools/testing/selftests/clone3/.gitignore >b/tools/testing/selftests/clone3/.gitignore >new file mode 100644 >index 000000000000..c63c64a78ddf >--- /dev/null >+++ b/tools/testing/selftests/clone3/.gitignore >@@ -0,0 +1,2 @@ >+clone3_set_tid >+clone3 >diff --git a/tools/testing/selftests/clone3/Makefile >b/tools/testing/selftests/clone3/Makefile >new file mode 100644 >index 000000000000..4efcf45b995b >--- /dev/null >+++ b/tools/testing/selftests/clone3/Makefile >@@ -0,0 +1,11 @@ >+# SPDX-License-Identifier: GPL-2.0 >+uname_M := $(shell uname -m 2>/dev/null || echo not) >+ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/) >+ >+CFLAGS += -I../../../../usr/include/ >+ >+ifeq ($(ARCH),x86_64) >+ TEST_GEN_PROGS := clone3 clone3_set_tid >+endif >+ >+include ../lib.mk >diff --git a/tools/testing/selftests/clone3/clone3.c >b/tools/testing/selftests/clone3/clone3.c >new file mode 100644 >index 000000000000..55a6915566b8 >--- /dev/null >+++ b/tools/testing/selftests/clone3/clone3.c >@@ -0,0 +1,141 @@ >+// SPDX-License-Identifier: GPL-2.0 >+ >+/* Based on Christian Brauner's clone3() example */ >+ >+#define _GNU_SOURCE >+#include <errno.h> >+#include <linux/types.h> >+#include <linux/sched.h> >+#include <stdio.h> >+#include <stdlib.h> >+#include <sys/syscall.h> >+#include <sys/types.h> >+#include <sys/un.h> >+#include <sys/wait.h> >+#include <unistd.h> >+#include <sched.h> >+ >+#include "../kselftest.h" >+ >+static pid_t raw_clone(struct clone_args *args) >+{ >+ return syscall(__NR_clone3, args, sizeof(struct clone_args)); >+} >+ >+static int call_clone3(int flags) >+{ >+ struct clone_args args = {0}; >+ pid_t ppid = -1; >+ pid_t pid = -1; >+ int status; >+ >+ args.flags = flags; >+ args.exit_signal = SIGCHLD; >+ >+ pid = raw_clone(&args); >+ if (pid < 0) { >+ ksft_print_msg("%s - Failed to create new process\n", >+ strerror(errno)); >+ return -errno; >+ } >+ >+ if (pid == 0) { >+ ksft_print_msg("I am the child, my PID is %d\n", getpid()); >+ _exit(EXIT_SUCCESS); >+ } >+ >+ ppid = getpid(); >+ ksft_print_msg("I am the parent (%d). My child's pid is %d\n", >+ ppid, pid); >+ >+ (void)wait(&status); >+ if (WEXITSTATUS(status)) >+ return WEXITSTATUS(status); >+ >+ return 0; >+} >+ >+static int test_clone3(int flags, int expected) >+{ >+ int ret; >+ >+ ksft_print_msg("[%d] Trying clone3() with flags 0x%x\n", >+ getpid(), flags); >+ ret = call_clone3(flags); >+ ksft_print_msg("[%d] clone3() with flags says :%d expected %d\n", >+ getpid(), ret, expected); >+ if (ret != expected) >+ ksft_exit_fail_msg( >+ "[%d] Result (%d) is different than expected (%d)\n", >+ getpid(), ret, expected); >+ ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n", >+ getpid(), ret, expected); >+ return 0; >+} >+int main(int argc, char *argv[]) >+{ >+ int ret = -1; >+ pid_t pid; >+ >+ ksft_print_header(); >+ ksft_set_plan(3); >+ >+ /* Just a simple clone3() should return 0.*/ >+ if (test_clone3(0, 0)) >+ goto on_error; >+ /* Do a clone3() in a new PID NS.*/ >+ if (test_clone3(CLONE_NEWPID, 0)) >+ goto on_error; >+ ksft_print_msg("First unshare\n"); >+ if (unshare(CLONE_NEWPID)) >+ goto on_error; >+ /* >+ * Before clone3()ing in a new PID NS with >+ * CLONE_NEWPID a fork() is necessary. >+ */ >+ if (test_clone3(CLONE_NEWPID, -EINVAL)) >+ goto on_error; >+ pid = fork(); >+ if (pid < 0) { >+ ksft_print_msg("First fork() failed\n"); >+ goto on_error; >+ } >+ if (pid > 0) { >+ (void)wait(NULL); >+ goto parent_out; >+ } >+ ksft_set_plan(6); >+ if (test_clone3(CLONE_NEWPID, 0)) >+ goto on_error; >+ if (test_clone3(0, 0)) >+ goto on_error; >+ ksft_print_msg("Second unshare\n"); >+ if (unshare(CLONE_NEWPID)) >+ goto on_error; >+ /* >+ * Before clone3()ing in a new PID NS with >+ * CLONE_NEWPID a fork() is necessary. >+ */ >+ if (test_clone3(CLONE_NEWPID, -EINVAL)) >+ goto on_error; >+ pid = fork(); >+ if (pid < 0) { >+ ksft_print_msg("Second fork() failed\n"); >+ goto on_error; >+ } >+ if (pid > 0) { >+ (void)wait(NULL); >+ goto parent_out; >+ } >+ ksft_set_plan(8); >+ if (test_clone3(CLONE_NEWPID, 0)) >+ goto on_error; >+ if (test_clone3(0, 0)) >+ goto on_error; >+ >+parent_out: >+ ret = 0; >+on_error: >+ >+ return !ret ? ksft_exit_pass() : ksft_exit_fail(); >+} >diff --git a/tools/testing/selftests/clone3/clone3_set_tid.c >b/tools/testing/selftests/clone3/clone3_set_tid.c >new file mode 100644 >index 000000000000..f5012e84dcb3 >--- /dev/null >+++ b/tools/testing/selftests/clone3/clone3_set_tid.c >@@ -0,0 +1,161 @@ >+// SPDX-License-Identifier: GPL-2.0 >+ >+/* Based on Christian Brauner's clone3() example */ >+ >+#define _GNU_SOURCE >+#include <errno.h> >+#include <linux/types.h> >+#include <linux/sched.h> >+#include <stdio.h> >+#include <stdlib.h> >+#include <sys/syscall.h> >+#include <sys/types.h> >+#include <sys/un.h> >+#include <sys/wait.h> >+#include <unistd.h> >+#include <sched.h> >+ >+#include "../kselftest.h" >+ >+static pid_t raw_clone(struct clone_args *args) >+{ >+ return syscall(__NR_clone3, args, sizeof(struct clone_args)); >+} >+ >+static int call_clone3_set_tid(int set_tid, int flags) >+{ >+ struct clone_args args = {0}; >+ pid_t ppid = -1; >+ pid_t pid = -1; >+ int status; >+ >+ args.flags = flags; >+ args.exit_signal = SIGCHLD; >+ args.set_tid = set_tid; >+ >+ pid = raw_clone(&args); >+ if (pid < 0) { >+ ksft_print_msg("%s - Failed to create new process\n", >+ strerror(errno)); >+ return -errno; >+ } >+ >+ if (pid == 0) { >+ ksft_print_msg("I am the child, my PID is %d (expected %d)\n", >+ getpid(), set_tid); >+ if (set_tid != getpid()) >+ _exit(EXIT_FAILURE); >+ _exit(EXIT_SUCCESS); >+ } >+ >+ ppid = getpid(); >+ ksft_print_msg("I am the parent (%d). My child's pid is %d\n", >+ ppid, pid); >+ >+ (void)wait(&status); >+ if (WEXITSTATUS(status)) >+ return WEXITSTATUS(status); >+ >+ return 0; >+} >+ >+static int test_clone3_set_tid(int set_tid, int flags, int expected) >+{ >+ int ret; >+ >+ ksft_print_msg( >+ "[%d] Trying clone3() with CLONE_SET_TID to %d and 0x%x\n", >+ getpid(), set_tid, flags); >+ ret = call_clone3_set_tid(set_tid, flags); >+ ksft_print_msg( >+ "[%d] clone3() with CLONE_SET_TID %d says :%d - expected %d\n", >+ getpid(), set_tid, ret, expected); >+ if (ret != expected) >+ ksft_exit_fail_msg( >+ "[%d] Result (%d) is different than expected (%d)\n", >+ getpid(), ret, expected); >+ ksft_test_result_pass("[%d] Result (%d) matches expectation (%d)\n", >+ getpid(), ret, expected); >+ return 0; >+} >+int main(int argc, char *argv[]) >+{ >+ FILE *f; >+ int pid_max = 0; >+ pid_t pid; >+ pid_t ns_pid; >+ int ret = -1; >+ >+ ksft_print_header(); >+ ksft_set_plan(13); >+ >+ f = fopen("/proc/sys/kernel/pid_max", "r"); >+ if (f == NULL) >+ ksft_exit_fail_msg( >+ "%s - Could not open /proc/sys/kernel/pid_max\n", >+ strerror(errno)); >+ fscanf(f, "%d", &pid_max); >+ fclose(f); >+ ksft_print_msg("/proc/sys/kernel/pid_max %d\n", pid_max); >+ >+ /* First try with an invalid PID */ >+ if (test_clone3_set_tid(-1, 0, -EINVAL)) >+ goto on_error; >+ if (test_clone3_set_tid(-1, CLONE_NEWPID, -EINVAL)) >+ goto on_error; >+ /* Then with PID 1 */ >+ if (test_clone3_set_tid(1, 0, -EEXIST)) >+ goto on_error; >+ /* PID 1 should not fail in a PID namespace */ >+ if (test_clone3_set_tid(1, CLONE_NEWPID, 0)) >+ goto on_error; >+ /* pid_max should fail everywhere */ >+ if (test_clone3_set_tid(pid_max, 0, -EINVAL)) >+ goto on_error; >+ if (test_clone3_set_tid(pid_max, CLONE_NEWPID, -EINVAL)) >+ goto on_error; >+ /* Find the current active PID */ >+ pid = fork(); >+ if (pid == 0) { >+ ksft_print_msg("Child has PID %d\n", getpid()); >+ sleep(1); >+ _exit(EXIT_SUCCESS); >+ } >+ /* Try to create a process with that PID should fail */ >+ if (test_clone3_set_tid(pid, 0, -EEXIST)) >+ goto on_error; >+ (void)wait(NULL); >+ /* After the child has finished, try again with the same PID */ >+ if (test_clone3_set_tid(pid, 0, 0)) >+ goto on_error; >+ /* This should fail as there is no PID 1 in that namespace */ >+ if (test_clone3_set_tid(pid, CLONE_NEWPID, -EINVAL)) >+ goto on_error; >+ unshare(CLONE_NEWPID); >+ if (test_clone3_set_tid(10, 0, -EINVAL)) >+ goto on_error; >+ /* Let's create a PID 1 */ >+ ns_pid = fork(); >+ if (ns_pid == 0) { >+ ksft_print_msg("Child in PID namespace has PID %d\n", getpid()); >+ sleep(1); >+ _exit(EXIT_SUCCESS); >+ } >+ /* >+ * Now, after the unshare() it should be possible to create a process >+ * with another ID than 1 in the PID namespace. >+ */ >+ if (test_clone3_set_tid(2, 0, 0)) >+ goto on_error; >+ /* Use a different PID in this namespace. */ >+ if (test_clone3_set_tid(2222, 0, 0)) >+ goto on_error; >+ if (test_clone3_set_tid(1, 0, -EEXIST)) >+ goto on_error; >+ (void)wait(NULL); >+ >+ ret = 0; >+on_error: >+ >+ return !ret ? ksft_exit_pass() : ksft_exit_fail(); >+} Thanks for the tests! Could you also add tests where we pass invalid or unknown struct sizes?: - pass struct size that is too small aka < CLONE3_ARGS_SIZE_V0 - pass a struct size that is too large aka > PAGE_SIZE - pass struct size that is smaller than the one the kernel supports - pass struct size that is larger than the one the kernel supports; once with all unknown fields set to 0 and once with a field set to non-0 I think this might fit well with this patch since it changes the struct size. :) Sorry, I didn't know you'd be sending out a new version today. :) Christian ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID 2019-08-11 20:33 [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Adrian Reber 2019-08-11 20:33 ` [PATCH v5 2/2] selftests: add tests for clone3() Adrian Reber @ 2019-08-12 9:40 ` Christian Brauner 2019-08-12 16:37 ` Oleg Nesterov 2 siblings, 0 replies; 8+ messages in thread From: Christian Brauner @ 2019-08-12 9:40 UTC (permalink / raw) To: Adrian Reber, Eric Biederman, Pavel Emelianov, Jann Horn, Oleg Nesterov, Dmitry Safonov Cc: linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov On August 11, 2019 10:33:26 PM GMT+02:00, Adrian Reber <areber@redhat.com> wrote: >The main motivation to add set_tid to clone3() is CRIU. > >To restore a process with the same PID/TID CRIU currently uses >/proc/sys/kernel/ns_last_pid. It writes the desired (PID - 1) to >ns_last_pid and then (quickly) does a clone(). This works most of the >time, but it is racy. It is also slow as it requires multiple syscalls. > >Extending clone3() to support set_tid makes it possible restore a >process using CRIU without accessing /proc/sys/kernel/ns_last_pid and >race free (as long as the desired PID/TID is available). > >This clone3() extension places the same restrictions (CAP_SYS_ADMIN) >on clone3() with set_tid as they are currently in place for >ns_last_pid. > >Signed-off-by: Adrian Reber <areber@redhat.com> >--- >v2: > - Removed (size < sizeof(struct clone_args)) as discussed with > Christian and Dmitry > - Added comment to ((set_tid != 1) && idr_get_cursor() <= 1) (Oleg) > - Use idr_alloc() instead of idr_alloc_cyclic() (Oleg) > >v3: > - Return EEXIST if PID is already in use (Christian) > - Drop CLONE_SET_TID (Christian and Oleg) > - Use idr_is_empty() instead of idr_get_cursor() (Oleg) > - Handle different `struct clone_args` sizes (Dmitry) > >v4: > - Rework struct size check with defines (Christian) > - Reduce number of set_tid checks (Oleg) > - Less parentheses and more robust code (Oleg) > - Do ns_capable() on correct user_ns (Oleg, Christian) > >v5: > - make set_tid checks earlier in alloc_pid() (Christian) > - remove unnecessary comment and struct size check (Christian) >--- > include/linux/pid.h | 2 +- > include/linux/sched/task.h | 1 + > include/uapi/linux/sched.h | 1 + > kernel/fork.c | 22 ++++++++++++++++++++-- > kernel/pid.c | 36 +++++++++++++++++++++++++++++------- > 5 files changed, 52 insertions(+), 10 deletions(-) > >diff --git a/include/linux/pid.h b/include/linux/pid.h >index 2a83e434db9d..052000db0ced 100644 >--- a/include/linux/pid.h >+++ b/include/linux/pid.h >@@ -116,7 +116,7 @@ extern struct pid *find_vpid(int nr); > extern struct pid *find_get_pid(int nr); > extern struct pid *find_ge_pid(int nr, struct pid_namespace *); > >-extern struct pid *alloc_pid(struct pid_namespace *ns); >+extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t set_tid); > extern void free_pid(struct pid *pid); > extern void disable_pid_allocation(struct pid_namespace *ns); > >diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h >index 0497091e40c1..4f2a80564332 100644 >--- a/include/linux/sched/task.h >+++ b/include/linux/sched/task.h >@@ -26,6 +26,7 @@ struct kernel_clone_args { > unsigned long stack; > unsigned long stack_size; > unsigned long tls; >+ pid_t set_tid; > }; > > /* >diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h >index b3105ac1381a..e1ce103a2c47 100644 >--- a/include/uapi/linux/sched.h >+++ b/include/uapi/linux/sched.h >@@ -45,6 +45,7 @@ struct clone_args { > __aligned_u64 stack; > __aligned_u64 stack_size; > __aligned_u64 tls; >+ __aligned_u64 set_tid; > }; > > /* >diff --git a/kernel/fork.c b/kernel/fork.c >index 2852d0e76ea3..0365041243b1 100644 >--- a/kernel/fork.c >+++ b/kernel/fork.c >@@ -117,6 +117,13 @@ > */ > #define MAX_THREADS FUTEX_TID_MASK > >+/* >+ * Different sizes of struct clone_args >+ */ >+#define CLONE3_ARGS_SIZE_V0 64 >+/* V1 includes set_tid */ >+#define CLONE3_ARGS_SIZE_V1 72 >+ > /* > * Protected counters by write_lock_irq(&tasklist_lock) > */ >@@ -2031,7 +2038,13 @@ static __latent_entropy struct task_struct >*copy_process( > stackleak_task_init(p); > > if (pid != &init_struct_pid) { >- pid = alloc_pid(p->nsproxy->pid_ns_for_children); >+ if (args->set_tid && !ns_capable( >+ p->nsproxy->pid_ns_for_children->user_ns, >+ CAP_SYS_ADMIN)) { >+ retval = -EPERM; >+ goto bad_fork_cleanup_thread; >+ } >+ pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid); > if (IS_ERR(pid)) { > retval = PTR_ERR(pid); > goto bad_fork_cleanup_thread; >@@ -2535,9 +2548,13 @@ noinline static int >copy_clone_args_from_user(struct kernel_clone_args *kargs, > if (unlikely(size > PAGE_SIZE)) > return -E2BIG; > >- if (unlikely(size < sizeof(struct clone_args))) >+ if (unlikely(size < CLONE3_ARGS_SIZE_V0)) > return -EINVAL; > >+ if (size < sizeof(struct clone_args)) >+ memset((void *)&args + size, 0, >+ sizeof(struct clone_args) - size); >+ > if (unlikely(!access_ok(uargs, size))) > return -EFAULT; > >@@ -2571,6 +2588,7 @@ noinline static int >copy_clone_args_from_user(struct kernel_clone_args *kargs, > .stack = args.stack, > .stack_size = args.stack_size, > .tls = args.tls, >+ .set_tid = args.set_tid, > }; > > return 0; >diff --git a/kernel/pid.c b/kernel/pid.c >index 0a9f2e437217..c3ce82f8206b 100644 >--- a/kernel/pid.c >+++ b/kernel/pid.c >@@ -157,7 +157,7 @@ void free_pid(struct pid *pid) > call_rcu(&pid->rcu, delayed_put_pid); > } > >-struct pid *alloc_pid(struct pid_namespace *ns) >+struct pid *alloc_pid(struct pid_namespace *ns, int set_tid) > { > struct pid *pid; > enum pid_type type; >@@ -166,6 +166,9 @@ struct pid *alloc_pid(struct pid_namespace *ns) > struct upid *upid; > int retval = -ENOMEM; > >+ if (set_tid < 0 || set_tid >= pid_max) >+ return ERR_PTR(-EINVAL); >+ > pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); > if (!pid) > return ERR_PTR(retval); >@@ -186,12 +189,31 @@ struct pid *alloc_pid(struct pid_namespace *ns) > if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS) > pid_min = RESERVED_PIDS; > >- /* >- * Store a null pointer so find_pid_ns does not find >- * a partially initialized PID (see below). >- */ >- nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min, >- pid_max, GFP_ATOMIC); >+ if (set_tid) { >+ /* >+ * Also fail if a PID != 1 is requested >+ * and no PID 1 exists. >+ */ >+ nr = -EINVAL; >+ if (set_tid == 1 || !idr_is_empty(&tmp->idr)) >+ nr = idr_alloc(&tmp->idr, NULL, set_tid, >+ set_tid + 1, GFP_ATOMIC); >+ /* >+ * If ENOSPC is returned it means that the PID is >+ * alreay in use. Return EEXIST in that case. >+ */ >+ if (nr == -ENOSPC) >+ nr = -EEXIST; >+ /* Only use set_tid for one PID namespace. */ >+ set_tid = 0; >+ } else { >+ /* >+ * Store a null pointer so find_pid_ns does not find >+ * a partially initialized PID (see below). >+ */ >+ nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min, >+ pid_max, GFP_ATOMIC); >+ } > spin_unlock_irq(&pidmap_lock); > idr_preload_end(); > Ah, one more nit, since I reckon you'll resend anyway because of the additional tests: The subject of the patch is not accurate anymore. Since we don't add a new flag but rather only a new argument referencing CLONE_SET_TID seems misleading. :) Christian ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID 2019-08-11 20:33 [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Adrian Reber 2019-08-11 20:33 ` [PATCH v5 2/2] selftests: add tests for clone3() Adrian Reber 2019-08-12 9:40 ` [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Christian Brauner @ 2019-08-12 16:37 ` Oleg Nesterov 2019-08-12 16:51 ` Christian Brauner 2 siblings, 1 reply; 8+ messages in thread From: Oleg Nesterov @ 2019-08-12 16:37 UTC (permalink / raw) To: Adrian Reber Cc: Christian Brauner, Eric Biederman, Pavel Emelianov, Jann Horn, Dmitry Safonov, linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov On 08/11, Adrian Reber wrote: > > include/linux/pid.h | 2 +- > include/linux/sched/task.h | 1 + > include/uapi/linux/sched.h | 1 + > kernel/fork.c | 22 ++++++++++++++++++++-- > kernel/pid.c | 36 +++++++++++++++++++++++++++++------- > 5 files changed, 52 insertions(+), 10 deletions(-) Looks good to me... A couple of nits below, but I won't insist, feel free to ignore. > +/* > + * Different sizes of struct clone_args > + */ > +#define CLONE3_ARGS_SIZE_V0 64 I don't really understand why do we want the "size < CLONE3_ARGS_SIZE_V0" check in copy_clone_args_from_user(), but I won't argue. > +/* V1 includes set_tid */ > +#define CLONE3_ARGS_SIZE_V1 72 unused? > @@ -2031,7 +2038,13 @@ static __latent_entropy struct task_struct *copy_process( > stackleak_task_init(p); > > if (pid != &init_struct_pid) { > - pid = alloc_pid(p->nsproxy->pid_ns_for_children); > + if (args->set_tid && !ns_capable( > + p->nsproxy->pid_ns_for_children->user_ns, > + CAP_SYS_ADMIN)) { > + retval = -EPERM; > + goto bad_fork_cleanup_thread; > + } > + pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid); copy_process() is already huge and complex, why not move this check into alloc_pid() ? Again, note that is accepts the same ->pid_ns_for_children. > @@ -166,6 +166,9 @@ struct pid *alloc_pid(struct pid_namespace *ns) > struct upid *upid; > int retval = -ENOMEM; > > + if (set_tid < 0 || set_tid >= pid_max) > + return ERR_PTR(-EINVAL); > + > pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); > if (!pid) > return ERR_PTR(retval); > @@ -186,12 +189,31 @@ struct pid *alloc_pid(struct pid_namespace *ns) > if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS) > pid_min = RESERVED_PIDS; > > - /* > - * Store a null pointer so find_pid_ns does not find > - * a partially initialized PID (see below). > - */ > - nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min, > - pid_max, GFP_ATOMIC); > + if (set_tid) { > + /* > + * Also fail if a PID != 1 is requested > + * and no PID 1 exists. > + */ > + nr = -EINVAL; > + if (set_tid == 1 || !idr_is_empty(&tmp->idr)) On the second thought, I think we should check ns->child_reaper != NULL rather than !idr_is_empty(), this looks more robust and clean. And this way alloc_pid() can do everything lockless at the start, if (set_tid) { if (set_tid < 0 || set_tid >= pid_max) return ERR_PTR(-EINVAL); if (set_tid != 1 && !ns->child_reaper) return ERR_PTR(-EINVAL); if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) return ERR_PTR(-EPERM); } and just for record... this is off-topic and I need to recheck, but today "ns->pid_allocated = 0" in free_pid() doesn't look right to me... This logic predates unshare(CLONE_PIDNS). Oleg. ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID 2019-08-12 16:37 ` Oleg Nesterov @ 2019-08-12 16:51 ` Christian Brauner 2019-08-12 16:57 ` Oleg Nesterov 0 siblings, 1 reply; 8+ messages in thread From: Christian Brauner @ 2019-08-12 16:51 UTC (permalink / raw) To: Oleg Nesterov Cc: Adrian Reber, Eric Biederman, Pavel Emelianov, Jann Horn, Dmitry Safonov, linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov On Mon, Aug 12, 2019 at 06:37:10PM +0200, Oleg Nesterov wrote: > On 08/11, Adrian Reber wrote: > > > > include/linux/pid.h | 2 +- > > include/linux/sched/task.h | 1 + > > include/uapi/linux/sched.h | 1 + > > kernel/fork.c | 22 ++++++++++++++++++++-- > > kernel/pid.c | 36 +++++++++++++++++++++++++++++------- > > 5 files changed, 52 insertions(+), 10 deletions(-) > > Looks good to me... > > A couple of nits below, but I won't insist, feel free to ignore. > > > +/* > > + * Different sizes of struct clone_args > > + */ > > +#define CLONE3_ARGS_SIZE_V0 64 > > I don't really understand why do we want the "size < CLONE3_ARGS_SIZE_V0" > check in copy_clone_args_from_user(), but I won't argue. To make sure a user can't give us a garbage sized struct that is smaller than the initial version of the struct. Hm, maybe you did make a suggestion how to detect this case that I missed in one of the previous reviews or why it's not needed? ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID 2019-08-12 16:51 ` Christian Brauner @ 2019-08-12 16:57 ` Oleg Nesterov 2019-08-12 17:05 ` Christian Brauner 0 siblings, 1 reply; 8+ messages in thread From: Oleg Nesterov @ 2019-08-12 16:57 UTC (permalink / raw) To: Christian Brauner Cc: Adrian Reber, Eric Biederman, Pavel Emelianov, Jann Horn, Dmitry Safonov, linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov On 08/12, Christian Brauner wrote: > On Mon, Aug 12, 2019 at 06:37:10PM +0200, Oleg Nesterov wrote: > > On 08/11, Adrian Reber wrote: > > > > > > include/linux/pid.h | 2 +- > > > include/linux/sched/task.h | 1 + > > > include/uapi/linux/sched.h | 1 + > > > kernel/fork.c | 22 ++++++++++++++++++++-- > > > kernel/pid.c | 36 +++++++++++++++++++++++++++++------- > > > 5 files changed, 52 insertions(+), 10 deletions(-) > > > > Looks good to me... > > > > A couple of nits below, but I won't insist, feel free to ignore. > > > > > +/* > > > + * Different sizes of struct clone_args > > > + */ > > > +#define CLONE3_ARGS_SIZE_V0 64 > > > > I don't really understand why do we want the "size < CLONE3_ARGS_SIZE_V0" > > check in copy_clone_args_from_user(), but I won't argue. > > To make sure a user can't give us a garbage sized struct that is smaller > than the initial version of the struct. But why do we want to detect this case? And why CLONE3_ARGS_SIZE_V0 is special? Oleg. ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID 2019-08-12 16:57 ` Oleg Nesterov @ 2019-08-12 17:05 ` Christian Brauner 0 siblings, 0 replies; 8+ messages in thread From: Christian Brauner @ 2019-08-12 17:05 UTC (permalink / raw) To: Oleg Nesterov Cc: Adrian Reber, Eric Biederman, Pavel Emelianov, Jann Horn, Dmitry Safonov, linux-kernel, Andrei Vagin, Mike Rapoport, Radostin Stoyanov On Mon, Aug 12, 2019 at 06:57:34PM +0200, Oleg Nesterov wrote: > On 08/12, Christian Brauner wrote: > > On Mon, Aug 12, 2019 at 06:37:10PM +0200, Oleg Nesterov wrote: > > > On 08/11, Adrian Reber wrote: > > > > > > > > include/linux/pid.h | 2 +- > > > > include/linux/sched/task.h | 1 + > > > > include/uapi/linux/sched.h | 1 + > > > > kernel/fork.c | 22 ++++++++++++++++++++-- > > > > kernel/pid.c | 36 +++++++++++++++++++++++++++++------- > > > > 5 files changed, 52 insertions(+), 10 deletions(-) > > > > > > Looks good to me... > > > > > > A couple of nits below, but I won't insist, feel free to ignore. > > > > > > > +/* > > > > + * Different sizes of struct clone_args > > > > + */ > > > > +#define CLONE3_ARGS_SIZE_V0 64 > > > > > > I don't really understand why do we want the "size < CLONE3_ARGS_SIZE_V0" > > > check in copy_clone_args_from_user(), but I won't argue. > > > > To make sure a user can't give us a garbage sized struct that is smaller > > than the initial version of the struct. > > But why do we want to detect this case? I have to admit I don't understand that question. Because it's a garbage sized struct that we can't do anything with. Why shouldn't we detect this case? > > And why CLONE3_ARGS_SIZE_V0 is special? Hm? Because that is the first-well known struct size. In fact this pattern is also used for perf and sched: if (!access_ok(uattr, PERF_ATTR_SIZE_VER0)) return -EFAULT; ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2019-08-12 17:06 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-08-11 20:33 [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Adrian Reber 2019-08-11 20:33 ` [PATCH v5 2/2] selftests: add tests for clone3() Adrian Reber 2019-08-11 21:37 ` Christian Brauner 2019-08-12 9:40 ` [PATCH v5 1/2] fork: extend clone3() to support CLONE_SET_TID Christian Brauner 2019-08-12 16:37 ` Oleg Nesterov 2019-08-12 16:51 ` Christian Brauner 2019-08-12 16:57 ` Oleg Nesterov 2019-08-12 17:05 ` Christian Brauner
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