From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
Simon Marchi <simon.marchi@efficios.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Pedro Alves <palves@redhat.com>,
Jan Kratochvil <jan.kratochvil@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.14 04/37] ptrace: make ptrace() fail if the tracee changed its pid unexpectedly
Date: Mon, 24 May 2021 17:25:08 +0200 [thread overview]
Message-ID: <20210524152324.341199460@linuxfoundation.org> (raw)
In-Reply-To: <20210524152324.199089755@linuxfoundation.org>
From: Oleg Nesterov <oleg@redhat.com>
[ Upstream commit dbb5afad100a828c97e012c6106566d99f041db6 ]
Suppose we have 2 threads, the group-leader L and a sub-theread T,
both parked in ptrace_stop(). Debugger tries to resume both threads
and does
ptrace(PTRACE_CONT, T);
ptrace(PTRACE_CONT, L);
If the sub-thread T execs in between, the 2nd PTRACE_CONT doesn not
resume the old leader L, it resumes the post-exec thread T which was
actually now stopped in PTHREAD_EVENT_EXEC. In this case the
PTHREAD_EVENT_EXEC event is lost, and the tracer can't know that the
tracee changed its pid.
This patch makes ptrace() fail in this case until debugger does wait()
and consumes PTHREAD_EVENT_EXEC which reports old_pid. This affects all
ptrace requests except the "asynchronous" PTRACE_INTERRUPT/KILL.
The patch doesn't add the new PTRACE_ option to not complicate the API,
and I _hope_ this won't cause any noticeable regression:
- If debugger uses PTRACE_O_TRACEEXEC and the thread did an exec
and the tracer does a ptrace request without having consumed
the exec event, it's 100% sure that the thread the ptracer
thinks it is targeting does not exist anymore, or isn't the
same as the one it thinks it is targeting.
- To some degree this patch adds nothing new. In the scenario
above ptrace(L) can fail with -ESRCH if it is called after the
execing sub-thread wakes the leader up and before it "steals"
the leader's pid.
Test-case:
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <errno.h>
#include <pthread.h>
#include <assert.h>
void *tf(void *arg)
{
execve("/usr/bin/true", NULL, NULL);
assert(0);
return NULL;
}
int main(void)
{
int leader = fork();
if (!leader) {
kill(getpid(), SIGSTOP);
pthread_t th;
pthread_create(&th, NULL, tf, NULL);
for (;;)
pause();
return 0;
}
waitpid(leader, NULL, WSTOPPED);
ptrace(PTRACE_SEIZE, leader, 0,
PTRACE_O_TRACECLONE | PTRACE_O_TRACEEXEC);
waitpid(leader, NULL, 0);
ptrace(PTRACE_CONT, leader, 0,0);
waitpid(leader, NULL, 0);
int status, thread = waitpid(-1, &status, 0);
assert(thread > 0 && thread != leader);
assert(status == 0x80137f);
ptrace(PTRACE_CONT, thread, 0,0);
/*
* waitid() because waitpid(leader, &status, WNOWAIT) does not
* report status. Why ????
*
* Why WEXITED? because we have another kernel problem connected
* to mt-exec.
*/
siginfo_t info;
assert(waitid(P_PID, leader, &info, WSTOPPED|WEXITED|WNOWAIT) == 0);
assert(info.si_pid == leader && info.si_status == 0x0405);
/* OK, it sleeps in ptrace(PTRACE_EVENT_EXEC == 0x04) */
assert(ptrace(PTRACE_CONT, leader, 0,0) == -1);
assert(errno == ESRCH);
assert(leader == waitpid(leader, &status, WNOHANG));
assert(status == 0x04057f);
assert(ptrace(PTRACE_CONT, leader, 0,0) == 0);
return 0;
}
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Simon Marchi <simon.marchi@efficios.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Pedro Alves <palves@redhat.com>
Acked-by: Simon Marchi <simon.marchi@efficios.com>
Acked-by: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/ptrace.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 43a283041296..b28f3c66c6fe 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -163,6 +163,21 @@ void __ptrace_unlink(struct task_struct *child)
spin_unlock(&child->sighand->siglock);
}
+static bool looks_like_a_spurious_pid(struct task_struct *task)
+{
+ if (task->exit_code != ((PTRACE_EVENT_EXEC << 8) | SIGTRAP))
+ return false;
+
+ if (task_pid_vnr(task) == task->ptrace_message)
+ return false;
+ /*
+ * The tracee changed its pid but the PTRACE_EVENT_EXEC event
+ * was not wait()'ed, most probably debugger targets the old
+ * leader which was destroyed in de_thread().
+ */
+ return true;
+}
+
/* Ensure that nothing can wake it up, even SIGKILL */
static bool ptrace_freeze_traced(struct task_struct *task)
{
@@ -173,7 +188,8 @@ static bool ptrace_freeze_traced(struct task_struct *task)
return ret;
spin_lock_irq(&task->sighand->siglock);
- if (task_is_traced(task) && !__fatal_signal_pending(task)) {
+ if (task_is_traced(task) && !looks_like_a_spurious_pid(task) &&
+ !__fatal_signal_pending(task)) {
task->state = __TASK_TRACED;
ret = true;
}
--
2.30.2
next prev parent reply other threads:[~2021-05-24 15:38 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-24 15:25 [PATCH 4.14 00/37] 4.14.234-rc1 review Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 01/37] openrisc: Fix a memory leak Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 02/37] RDMA/rxe: Clear all QP fields if creation failed Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 03/37] scsi: qla2xxx: Fix error return code in qla82xx_write_flash_dword() Greg Kroah-Hartman
2021-05-24 15:25 ` Greg Kroah-Hartman [this message]
2021-05-24 15:25 ` [PATCH 4.14 05/37] cifs: fix memory leak in smb2_copychunk_range Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 06/37] ALSA: line6: Fix racy initialization of LINE6 MIDI Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 07/37] ALSA: usb-audio: Validate MS endpoint descriptors Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 08/37] ALSA: bebob/oxfw: fix Kconfig entry for Mackie d.2 Pro Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 09/37] Revert "ALSA: sb8: add a check for request_region" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 10/37] ALSA: hda/realtek: reset eapd coeff to default value for alc287 Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 11/37] Revert "rapidio: fix a NULL pointer dereference when create_workqueue() fails" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 12/37] rapidio: handle create_workqueue() failure Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 13/37] xen-pciback: reconfigure also from backend watch handler Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 14/37] dm snapshot: fix a crash when an origin has no snapshots Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 15/37] dm snapshot: fix crash with transient storage and zero chunk size Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 16/37] Revert "video: hgafb: fix potential NULL pointer dereference" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 17/37] Revert "net: stmicro: fix a missing check of clk_prepare" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 18/37] Revert "leds: lp5523: fix a missing check of return value of lp55xx_read" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 19/37] Revert "hwmon: (lm80) fix a missing check of bus read in lm80 probe" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 20/37] Revert "video: imsttfb: fix potential NULL pointer dereferences" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 21/37] Revert "ecryptfs: replace BUG_ON with error handling code" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 22/37] Revert "gdrom: fix a memory leak bug" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 23/37] cdrom: gdrom: deallocate struct gdrom_unit fields in remove_gdrom Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 24/37] cdrom: gdrom: initialize global variable at init time Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 25/37] Revert "media: rcar_drif: fix a memory disclosure" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 26/37] Revert "rtlwifi: fix a potential NULL pointer dereference" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 27/37] Revert "qlcnic: Avoid " Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 28/37] Revert "niu: fix missing checks of niu_pci_eeprom_read" Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 29/37] ethernet: sun: niu: fix missing checks of niu_pci_eeprom_read() Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 30/37] net: stmicro: handle clk_prepare() failure during init Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 31/37] net: rtlwifi: properly check for alloc_workqueue() failure Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 32/37] leds: lp5523: check return value of lp5xx_read and jump to cleanup code Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 33/37] qlcnic: Add null check after calling netdev_alloc_skb Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 34/37] video: hgafb: fix potential NULL pointer dereference Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 35/37] vgacon: Record video mode changes with VT_RESIZEX Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 36/37] vt: Fix character height handling " Greg Kroah-Hartman
2021-05-24 15:25 ` [PATCH 4.14 37/37] tty: vt: always invoke vc->vc_sw->con_resize callback Greg Kroah-Hartman
2021-05-25 0:55 ` [PATCH 4.14 00/37] 4.14.234-rc1 review Samuel Zou
2021-05-25 12:06 ` Naresh Kamboju
2021-05-25 21:23 ` Guenter Roeck
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