Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1484683

[PATCH v2 6/8] lib/syscall: Pin the task stack in collect_syscall()

Show all headers | View raw

This will avoid a potential read-after-free if collect_syscall()
(e.g. /proc/PID/syscall) is called on an exiting task.

Reported-by: Jann Horn <jann@thejh.net>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 lib/syscall.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/syscall.c b/lib/syscall.c
index e30e03932480..63239e097b13 100644
--- a/lib/syscall.c
+++ b/lib/syscall.c
@@ -7,9 +7,19 @@ static int collect_syscall(struct task_struct *target, long *callno,
 			   unsigned long args[6], unsigned int maxargs,
 			   unsigned long *sp, unsigned long *pc)
 {
-	struct pt_regs *regs = task_pt_regs(target);
-	if (unlikely(!regs))
+	struct pt_regs *regs;
+
+	if (!try_get_task_stack(target)) {
+		/* Task has no stack, so the task isn't in a syscall. */
+		*callno = -1;
+		return 0;
+	}
+
+	regs = task_pt_regs(target);
+	if (unlikely(!regs)) {
+		put_task_stack(target);
 		return -EAGAIN;
+	}
 
 	*sp = user_stack_pointer(regs);
 	*pc = instruction_pointer(regs);
@@ -18,6 +28,7 @@ static int collect_syscall(struct task_struct *target, long *callno,
 	if (*callno != -1L && maxargs > 0)
 		syscall_get_arguments(target, regs, 0, maxargs, args);
 
+	put_task_stack(target);
 	return 0;
 }
 
-- 
2.7.4

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v2 0/8] thread_info cleanups and stack caching Andy Lutomirski <luto@kernel.org> - 2016-09-16 07:50 +0200
  [PATCH v2 1/8] x86/entry/64: Fix a minor comment rebase error Andy Lutomirski <luto@kernel.org> - 2016-09-16 07:50 +0200
    [tip:x86/asm] x86/entry/64: Fix a minor comment rebase error tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-16 11:20 +0200
  [PATCH v2 4/8] x86/dumpstack: Pin the target stack when dumping it Andy Lutomirski <luto@kernel.org> - 2016-09-16 07:50 +0200
    [tip:x86/asm] x86/dumpstack: Pin the target stack when dumping it tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-16 11:20 +0200
      Re: [tip:x86/asm] x86/dumpstack: Pin the target stack when dumping it Josh Poimboeuf <jpoimboe@redhat.com> - 2016-09-16 14:00 +0200
        Re: [tip:x86/asm] x86/dumpstack: Pin the target stack when dumping it Josh Poimboeuf <jpoimboe@redhat.com> - 2016-09-16 14:30 +0200
          Re: [tip:x86/asm] x86/dumpstack: Pin the target stack when dumping it Ingo Molnar <mingo@kernel.org> - 2016-09-16 15:00 +0200
            [PATCH] x86/dumpstack: remove NULL task pointer convention Josh Poimboeuf <jpoimboe@redhat.com> - 2016-09-16 15:10 +0200
  [PATCH v2 6/8] lib/syscall: Pin the task stack in collect_syscall() Andy Lutomirski <luto@kernel.org> - 2016-09-16 07:50 +0200
    [tip:x86/asm] lib/syscall: Pin the task stack in collect_syscall() tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-16 11:20 +0200
  [PATCH v2 8/8] fork: Cache two thread stacks per cpu if CONFIG_VMAP_STACK is set Andy Lutomirski <luto@kernel.org> - 2016-09-16 07:50 +0200
    [tip:x86/asm] fork: Optimize task creation by caching two thread  stacks per CPU if CONFIG_VMAP_STACK=y tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-16 11:30 +0200
  [PATCH v2 3/8] kthread: to_live_kthread() needs try_get_task_stack() Andy Lutomirski <luto@kernel.org> - 2016-09-16 07:50 +0200
    [tip:x86/asm] kthread: Pin the stack via  try_get_task_stack()/put_task_stack() in to_live_kthread() function tip-bot for Oleg Nesterov <tipbot@zytor.com> - 2016-09-16 11:20 +0200

csiph-web