Commit 73af963f authored by Mark Grondona's avatar Mark Grondona Committed by Linus Torvalds
Browse files

__ptrace_may_access() should not deny sub-threads



__ptrace_may_access() checks get_dumpable/ptrace_has_cap/etc if task !=
current, this can can lead to surprising results.

For example, a sub-thread can't readlink("/proc/self/exe") if the
executable is not readable.  setup_new_exec()->would_dump() notices that
inode_permission(MAY_READ) fails and then it does
set_dumpable(suid_dumpable).  After that get_dumpable() fails.

(It is not clear why proc_pid_readlink() checks get_dumpable(), perhaps we
could add PTRACE_MODE_NODUMPABLE)

Change __ptrace_may_access() to use same_thread_group() instead of "task
== current".  Any security check is pointless when the tasks share the
same ->mm.
Signed-off-by: default avatarMark Grondona <mgrondona@llnl.gov>
Signed-off-by: default avatarBen Woodard <woodard@redhat.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b4c1107c
......@@ -236,7 +236,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
*/
int dumpable = 0;
/* Don't let security modules deny introspection */
if (task == current)
if (same_thread_group(task, current))
return 0;
rcu_read_lock();
tcred = __task_cred(task);
......
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