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From: benjamin@sipsolutions.net
To: linux-um@lists.infradead.org
Cc: Benjamin Berg <benjamin@sipsolutions.net>
Subject: [PATCH v2 28/28] um: Delay flushing syscalls until the thread is restarted
Date: Tue, 22 Nov 2022 11:07:59 +0100	[thread overview]
Message-ID: <20221122100759.208290-29-benjamin@sipsolutions.net> (raw)
In-Reply-To: <20221122100759.208290-1-benjamin@sipsolutions.net>

From: Benjamin Berg <benjamin@sipsolutions.net>

This way we can avoid doing two extra context switches when managing
processes using seccomp.

Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
---
 arch/um/include/shared/os.h        |  1 +
 arch/um/include/shared/skas/skas.h |  1 +
 arch/um/kernel/skas/process.c      |  8 ++++
 arch/um/kernel/tlb.c               | 10 +----
 arch/um/os-Linux/skas/mem.c        | 71 ++++++++++++++++--------------
 arch/um/os-Linux/skas/process.c    | 26 ++++++++++-
 6 files changed, 75 insertions(+), 42 deletions(-)

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 07683f45d7e1..aa888d4870d9 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -273,6 +273,7 @@ int syscall_stub_flush(struct mm_id *mm_idp);
 struct stub_syscall *syscall_stub_alloc(struct mm_id *mm_idp,
 					unsigned long data_len,
 					unsigned long *data_addr);
+void syscall_stub_dump_error(struct mm_id *mm_idp);
 
 void map(struct mm_id *mm_idp, unsigned long virt,
 	 unsigned long len, int prot, int phys_fd,
diff --git a/arch/um/include/shared/skas/skas.h b/arch/um/include/shared/skas/skas.h
index f10599995d4d..bc672d607101 100644
--- a/arch/um/include/shared/skas/skas.h
+++ b/arch/um/include/shared/skas/skas.h
@@ -21,5 +21,6 @@ extern void new_thread_handler(void);
 extern void handle_syscall(struct uml_pt_regs *regs);
 extern long execute_syscall_skas(void *r);
 extern unsigned long current_stub_stack(void);
+extern struct mm_id *current_mm_id(void);
 
 #endif
diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index f2ac134c9752..c7345c83e07b 100644
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -53,3 +53,11 @@ unsigned long current_stub_stack(void)
 
 	return current->mm->context.id.stack;
 }
+
+struct mm_id *current_mm_id(void)
+{
+	if (current->mm == NULL)
+		return NULL;
+
+	return &current->mm->context.id;
+}
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index c15cac380fcd..bda516cb1186 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -460,7 +460,7 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long address)
 	pmd_t *pmd;
 	pte_t *pte;
 	struct mm_struct *mm = vma->vm_mm;
-	int r, w, x, prot, err = 0;
+	int r, w, x, prot;
 	struct mm_id *mm_id;
 
 	address &= PAGE_MASK;
@@ -508,14 +508,6 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long address)
 	} else if (pte_newprot(*pte))
 		protect(mm_id, address, PAGE_SIZE, prot);
 
-	err = syscall_stub_flush(mm_id);
-	if (err) {
-		if (err == -ENOMEM)
-			report_enomem();
-
-		goto kill;
-	}
-
 	*pte = pte_mkuptodate(*pte);
 
 	return;
diff --git a/arch/um/os-Linux/skas/mem.c b/arch/um/os-Linux/skas/mem.c
index 619035151bc6..68155aadea09 100644
--- a/arch/um/os-Linux/skas/mem.c
+++ b/arch/um/os-Linux/skas/mem.c
@@ -25,6 +25,44 @@ extern char __syscall_stub_start[];
 extern void wait_stub_done(int pid);
 void wait_stub_done_seccomp(int pid, struct stub_data *data, int running);
 
+void syscall_stub_dump_error(struct mm_id *mm_idp)
+{
+	struct stub_data *proc_data = (void *)mm_idp->stack;
+	struct stub_syscall *sc;
+	int n;
+
+	if (proc_data->syscall_data_len < 0 ||
+	    proc_data->syscall_data_len > (long) mm_idp->syscall_data_len - sizeof(*sc))
+		panic("Syscall data was corrupted by stub (len is: %d, expected maximum: %d)!",
+		      proc_data->syscall_data_len,
+		      mm_idp->syscall_data_len);
+
+	sc = (void *) (((unsigned long) &proc_data->syscall_data) +
+		       proc_data->syscall_data_len);
+
+	printk(UM_KERN_ERR "%s : length = %d, last offset = %d",
+	       __func__, mm_idp->syscall_data_len,
+	       proc_data->syscall_data_len);
+	printk(UM_KERN_ERR "%s : syscall %ld failed, return value = 0x%lx, expected return value = 0x%lx\n",
+	       __func__, sc->syscall, proc_data->err,
+	       sc->expected_result);
+
+	printk(UM_KERN_ERR "    syscall parameters: 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n",
+	       sc->arg[0], sc->arg[1], sc->arg[2],
+	       sc->arg[3], sc->arg[4], sc->arg[5]);
+
+	n = sc->cmd_len - sizeof(*sc);
+	if (n > 0) {
+		printk(UM_KERN_ERR "    syscall data 0x%lx + %d",
+		       STUB_DATA + ((unsigned long) (&sc->data) &
+				    (UM_KERN_PAGE_SIZE - 1)),
+		       n);
+		print_hex_dump(UM_KERN_ERR,
+			       "    syscall data: ", 0,
+			       16, 4, sc->data, n, 0);
+	}
+}
+
 static inline unsigned long *check_init_stack(struct mm_id *mm_idp,
 					      unsigned long *stack)
 {
@@ -90,38 +128,7 @@ static inline long do_syscall_stub(struct mm_id *mm_idp)
 	 * otherwise it will be zero (but we do not need to rely on that).
 	 */
 	if (proc_data->err) {
-		struct stub_syscall *sc;
-
-		if (proc_data->syscall_data_len < 0 ||
-		    proc_data->syscall_data_len > (long) mm_idp->syscall_data_len - sizeof(*sc))
-			panic("Syscall data was corrupted by stub (len is: %d, expected maximum: %d)!",
-			      proc_data->syscall_data_len,
-			      mm_idp->syscall_data_len);
-
-		sc = (void *) (((unsigned long) &proc_data->syscall_data) +
-			       proc_data->syscall_data_len);
-
-		printk(UM_KERN_ERR "%s : length = %d, last offset = %d",
-		       __func__, mm_idp->syscall_data_len,
-		       proc_data->syscall_data_len);
-		printk(UM_KERN_ERR "%s : syscall %ld failed, return value = 0x%lx, expected return value = 0x%lx\n",
-		       __func__, sc->syscall, proc_data->err,
-		       sc->expected_result);
-
-		printk(UM_KERN_ERR "    syscall parameters: 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n",
-		       sc->arg[0], sc->arg[1], sc->arg[2],
-		       sc->arg[3], sc->arg[4], sc->arg[5]);
-
-		n = sc->cmd_len - sizeof(*sc);
-		if (n > 0) {
-			printk(UM_KERN_ERR "    syscall data 0x%lx + %d",
-			       STUB_DATA + ((unsigned long) (&sc->data) &
-					    (UM_KERN_PAGE_SIZE - 1)),
-			       n);
-			print_hex_dump(UM_KERN_ERR,
-				       "    syscall data: ", 0,
-				       16, 4, sc->data, n, 0);
-		}
+		syscall_stub_dump_error(mm_idp);
 
 		/* Store error code in case someone tries to add more syscalls */
 		mm_idp->syscall_data_len = proc_data->err;
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 55868eb35727..39941d14bb51 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -530,7 +530,8 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 			fatal_sigsegv();
 
 		if (using_seccomp) {
-			struct stub_data *proc_data = (void *)current_stub_stack();
+			struct mm_id *mm_id = current_mm_id();
+			struct stub_data *proc_data = (void *) mm_id->stack;
 			int ret;
 
 			ret = set_stub_state(regs, proc_data, singlestepping());
@@ -544,6 +545,10 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 			if (proc_data->restart_wait != 0)
 				panic("Programming error: Flag to only run syscalls in child was not cleared!");
 
+			/* Mark pending syscalls for flushing */
+			proc_data->syscall_data_len = mm_id->syscall_data_len;
+			mm_id->syscall_data_len = 0;
+
 			proc_data->signal = 0;
 			proc_data->futex = FUTEX_IN_CHILD;
 			CATCH_EINTR(syscall(__NR_futex, &proc_data->futex,
@@ -556,6 +561,13 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 
 			sig = proc_data->signal;
 
+			if (sig == SIGTRAP && proc_data->err != 0) {
+				printk(UM_KERN_ERR "%s - Error flushing stub syscalls",
+				       __func__);
+				syscall_stub_dump_error(mm_id);
+				fatal_sigsegv();
+			}
+
 			ret = get_stub_state(regs, proc_data);
 			if (ret) {
 				printk(UM_KERN_ERR "%s - failed to get regs: %d",
@@ -586,6 +598,14 @@ void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs)
 				GET_FAULTINFO_FROM_MC(regs->faultinfo, mcontext);
 			}
 		} else {
+			/* With ptrace, we need to explicitly flush all pending syscalls. */
+			err = syscall_stub_flush(current_mm_id());
+			if (err) {
+				printk(UM_KERN_ERR "%s - Error flushing stub syscalls: %d",
+				       __func__, -err);
+				fatal_sigsegv();
+			}
+
 			/*
 			 * This can legitimately fail if the process loads a
 			 * bogus value into a segment register.  It will
@@ -760,6 +780,10 @@ int copy_context_skas0(struct mm_id *id, struct mm_id *from)
 
 	child_data->child_err = -ESRCH;
 
+	err = syscall_stub_flush(from);
+	if (err)
+		return err;
+
 	if (using_seccomp) {
 		err = set_stub_state(&thread_regs, data, 0);
 		if (err)
-- 
2.38.1


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      parent reply	other threads:[~2022-11-22 10:26 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-22 10:07 [PATCH v2 00/28] Implement SECCOMP based userland benjamin
2022-11-22 10:07 ` [PATCH v2 01/28] um: Switch printk calls to adhere to correct coding style benjamin
2022-11-22 10:07 ` [PATCH v2 02/28] um: Declare fix_range_common as a static function benjamin
2022-11-22 10:07 ` [PATCH v2 03/28] um: Drop support for hosts without SYSEMU_SINGLESTEP support benjamin
2022-11-22 10:07 ` [PATCH v2 04/28] um: Drop NULL check from start_userspace benjamin
2022-11-22 10:07 ` [PATCH v2 05/28] um: Make errors to stop ptraced child fatal during startup benjamin
2022-11-22 10:07 ` [PATCH v2 06/28] um: Don't use vfprintf() for os_info() benjamin
2022-11-22 10:07 ` [PATCH v2 07/28] um: Do not use printk in SIGWINCH helper thread benjamin
2022-11-22 10:07 ` [PATCH v2 08/28] um: Reap winch thread if it fails benjamin
2022-11-22 10:07 ` [PATCH v2 09/28] um: Do not use printk in userspace trampoline benjamin
2022-11-22 10:07 ` [PATCH v2 10/28] um: Always inline stub functions benjamin
2022-11-22 10:07 ` [PATCH v2 11/28] um: Rely on PTRACE_SETREGSET to set FS/GS base registers benjamin
2022-11-22 10:07 ` [PATCH v2 12/28] um: Remove unused register save/restore functions benjamin
2022-11-22 10:07 ` [PATCH v2 13/28] um: Mark 32bit syscall helpers as clobbering memory benjamin
2022-11-22 10:07 ` [PATCH v2 14/28] um: Remove stub-data.h include from common-offsets.h benjamin
2022-11-22 10:07 ` [PATCH v2 15/28] um: Create signal stack memory assignment in stub_data benjamin
2022-11-22 10:07 ` [PATCH v2 16/28] um: Add generic stub_syscall6 function benjamin
2022-11-22 10:07 ` [PATCH v2 17/28] um: Rework syscall handling benjamin
2022-11-22 10:07 ` [PATCH v2 18/28] um: Store full CSGSFS and SS register from mcontext benjamin
2022-11-22 10:07 ` [PATCH v2 19/28] um: Pass full mm_id to functions creating helper processes benjamin
2022-11-22 10:07 ` [PATCH v2 20/28] um: Move faultinfo extraction into userspace routine benjamin
2022-11-22 10:07 ` [PATCH v2 21/28] um: Use struct uml_pt_regs for copy_context_skas0 benjamin
2022-11-22 10:07 ` [PATCH v2 22/28] um: Add UML_SECCOMP configuration option benjamin
2022-11-22 10:07 ` [PATCH v2 23/28] um: Add stub side of SECCOMP/futex based process handling benjamin
2022-11-22 10:07 ` [PATCH v2 24/28] um: Add helper functions to get/set state for SECCOMP benjamin
2022-11-22 10:07 ` [PATCH v2 25/28] um: Add SECCOMP support detection and initialization benjamin
2022-11-22 10:07 ` [PATCH v2 26/28] um: Die if a child dies unexpectedly in seccomp mode benjamin
2022-11-22 10:07 ` [PATCH v2 27/28] um: Implement kernel side of SECCOMP based process handling benjamin
2022-11-22 10:07 ` benjamin [this message]

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