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authorKees Cook <keescook@chromium.org>2017-11-29 16:10:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-29 18:40:42 -0800
commit04e35f4495dd560db30c25efca4eecae8ec8c375 (patch)
tree62d890cff810621d1143f601df6181384fb87a86
parent5f1d43de54164dcfb9bfa542fcc92c1e1a1b6c1d (diff)
exec: avoid RLIMIT_STACK races with prlimit()
While the defense-in-depth RLIMIT_STACK limit on setuid processes was protected against races from other threads calling setrlimit(), I missed protecting it against races from external processes calling prlimit(). This adds locking around the change and makes sure that rlim_max is set too. Link: http://lkml.kernel.org/r/20171127193457.GA11348@beast Fixes: 64701dee4178e ("exec: Use sane stack rlimit under secureexec") Signed-off-by: Kees Cook <keescook@chromium.org> Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Reported-by: Brad Spengler <spender@grsecurity.net> Acked-by: Serge Hallyn <serge@hallyn.com> Cc: James Morris <james.l.morris@oracle.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/exec.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 1d6243d9f2b6..6be2aa0ab26f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1340,10 +1340,15 @@ void setup_new_exec(struct linux_binprm * bprm)
* avoid bad behavior from the prior rlimits. This has to
* happen before arch_pick_mmap_layout(), which examines
* RLIMIT_STACK, but after the point of no return to avoid
- * needing to clean up the change on failure.
+ * races from other threads changing the limits. This also
+ * must be protected from races with prlimit() calls.
*/
+ task_lock(current->group_leader);
if (current->signal->rlim[RLIMIT_STACK].rlim_cur > _STK_LIM)
current->signal->rlim[RLIMIT_STACK].rlim_cur = _STK_LIM;
+ if (current->signal->rlim[RLIMIT_STACK].rlim_max > _STK_LIM)
+ current->signal->rlim[RLIMIT_STACK].rlim_max = _STK_LIM;
+ task_unlock(current->group_leader);
}
arch_pick_mmap_layout(current->mm);