Reset current->pdeath_signal on SUID binary execution

This fixes a vulnerability in the "parent process death signal"
implementation discoverd by Wojciech Purczynski of COSEINC PTE Ltd.
and iSEC Security Research.

http://marc.info/?l=bugtraq&m=118711306802632&w=2

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 7bdea7937ee8..ce62f7b65f17 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1084,9 +1084,12 @@ int flush_old_exec(struct linux_binprm * bprm)
          */
         current->mm->task_size = TASK_SIZE;
 
-        if (bprm->e_uid != current->euid || bprm->e_gid != current->egid || 
-            file_permission(bprm->file, MAY_READ) ||
-            (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
+        if (bprm->e_uid != current->euid || bprm->e_gid != current->egid) {
+                suid_keys(current);
+                set_dumpable(current->mm, suid_dumpable);
+                current->pdeath_signal = 0;
+        } else if (file_permission(bprm->file, MAY_READ) ||
+                        (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
                 suid_keys(current);
                 set_dumpable(current->mm, suid_dumpable);
         }
@@ -1177,8 +1180,10 @@ void compute_creds(struct linux_binprm *bprm)
 {
         int unsafe;
 
-        if (bprm->e_uid != current->uid)
+        if (bprm->e_uid != current->uid) {
                 suid_keys(current);
+                current->pdeath_signal = 0;
+        }
         exec_keys(current);
 
         task_lock(current);