diff options
| author | Andy Lutomirski <luto@kernel.org> | 2016-09-15 22:45:47 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-09-16 09:18:53 +0200 |
| commit | aa1f1a639621672b68f654dc815a7d8298ff396f (patch) | |
| tree | cf72e7859a0fbc24bb11aac984946383f6eb0aba /lib/syscall.c | |
| parent | 74327a3e884a0ff895ba7b51d3488e6a177407b2 (diff) | |
| download | lwn-aa1f1a639621672b68f654dc815a7d8298ff396f.tar.gz lwn-aa1f1a639621672b68f654dc815a7d8298ff396f.zip | |
lib/syscall: Pin the task stack in collect_syscall()
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>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/0bfd8e6d4729c97745d3781a29610a33d0a8091d.1474003868.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'lib/syscall.c')
| -rw-r--r-- | lib/syscall.c | 15 |
1 files 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; } |