path: root/kernel/ptrace.c
diff options
authorOleg Nesterov <oleg@redhat.com>2009-04-13 14:40:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-13 15:04:31 -0700
commitf1671f6d783a2385d32e11f456cbe32f0e4b4b49 (patch)
tree3d2dd4672db69b9d3b7f35e06b0fb90ca4d8cc12 /kernel/ptrace.c
parent7b102d034c0affc6ee703b576f2496ec6cb81d79 (diff)
ptrace: fix exit_ptrace() vs ptrace_traceme() race
Pointed out by Roland. The bug was recently introduced by me in "forget_original_parent: split out the un-ptrace part", commit 39c626ae47c469abdfd30c6e42eff884931380d6. Since that patch we have a window after exit_ptrace() drops tasklist and before forget_original_parent() takes it again. In this window the child can do ptrace(PTRACE_TRACEME) and nobody can untrace this child after that. Change ptrace_traceme() to not attach to the exiting ->real_parent. We don't report the error in this case, we pretend we attach right before ->real_parent calls exit_ptrace() which should untrace us anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Roland McGrath <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/ptrace.c')
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 64191fa09b7..dfcd83ceee3 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -604,10 +604,11 @@ repeat:
ret = security_ptrace_traceme(current->parent);
- * Set the ptrace bit in the process ptrace flags.
- * Then link us on our parent's ptraced list.
+ * Check PF_EXITING to ensure ->real_parent has not passed
+ * exit_ptrace(). Otherwise we don't report the error but
+ * pretend ->real_parent untraces us right after return.
- if (!ret) {
+ if (!ret && !(current->real_parent->flags & PF_EXITING)) {
current->ptrace |= PT_PTRACED;
__ptrace_link(current, current->real_parent);