Messages in this thread Patch in this message | | | Date | Thu, 23 Mar 2017 15:46:16 -0700 | From | Kees Cook <> | Subject | [PATCH] lib/syscall: Clear return values when no stack |
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Commit aa1f1a639621 ("lib/syscall: Pin the task stack in collect_syscall()") added logic to handle a process stack not existing, but left sp and pc uninitialized, which can be later reported via /proc/$pid/syscall for zombie processes, potentially exposing kernel memory to userspace.
Zombie /proc/$pid/syscall before: -1 0xffffffff9a060100 0xffff92f42d6ad900
Zombie /proc/$pid/syscall after: -1 0x0 0x0
Reported-by: Robert Święcki <robert@swiecki.net> Fixes: aa1f1a639621 ("lib/syscall: Pin the task stack in collect_syscall()") Cc: stable@vger.kernel.org # v4.9+ Signed-off-by: Kees Cook <keescook@chromium.org> --- lib/syscall.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/lib/syscall.c b/lib/syscall.c index 17d5ff5fa6a3..2c6cd1b5c3ea 100644 --- a/lib/syscall.c +++ b/lib/syscall.c @@ -12,6 +12,7 @@ static int collect_syscall(struct task_struct *target, long *callno, if (!try_get_task_stack(target)) { /* Task has no stack, so the task isn't in a syscall. */ + *sp = *pc = 0; *callno = -1; return 0; } -- 2.7.4
-- Kees Cook Pixel Security
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