Messages in this thread Patch in this message | | | Date | Thu, 23 Mar 2017 23:45:56 -0700 | From | tip-bot for Kees Cook <> | Subject | [tip:core/urgent] lib/syscall: Clear return values when no stack |
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Commit-ID: 854fbd6e5f60fe99e8e3a569865409fca378f143 Gitweb: http://git.kernel.org/tip/854fbd6e5f60fe99e8e3a569865409fca378f143 Author: Kees Cook <keescook@chromium.org> AuthorDate: Thu, 23 Mar 2017 15:46:16 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Fri, 24 Mar 2017 07:43:35 +0100
lib/syscall: Clear return values when no stack
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> Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-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> Cc: stable@vger.kernel.org # v4.9+ Fixes: aa1f1a639621 ("lib/syscall: Pin the task stack in collect_syscall()") Link: http://lkml.kernel.org/r/20170323224616.GA92694@beast Signed-off-by: Ingo Molnar <mingo@kernel.org> --- lib/syscall.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/lib/syscall.c b/lib/syscall.c index 17d5ff5..2c6cd1b 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; }
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