diff options
author | Oleg Nesterov <oleg@redhat.com> | 2013-09-11 17:24:37 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-11 18:59:03 -0400 |
commit | 96d0df79f2644fc823f26c06491e182d87a90c2a (patch) | |
tree | 09f0d82a4ac4e0410a0067466eb04ab138db3e4f | |
parent | a3c039929d01f793c47922017b6c0ae438e11598 (diff) |
proc: make proc_fd_permission() thread-friendly
proc_fd_permission() says "process can still access /proc/self/fd after it
has executed a setuid()", but the "task_pid() = proc_pid() check only
helps if the task is group leader, /proc/self points to
/proc/<leader-pid>.
Change this check to use task_tgid() so that the whole thread group can
access its /proc/self/fd or /proc/<tid-of-sub-thread>/fd.
Notes:
- CLONE_THREAD does not require CLONE_FILES so task->files
can differ, but I don't think this can lead to any security
problem. And this matches same_thread_group() in
__ptrace_may_access().
- /proc/self should probably point to /proc/<thread-tid>, but
it is too late to change the rules. Perhaps it makes sense
to add /proc/thread though.
Test-case:
void *tfunc(void *arg)
{
assert(opendir("/proc/self/fd"));
return NULL;
}
int main(void)
{
pthread_t t;
pthread_create(&t, NULL, tfunc, NULL);
pthread_join(t, NULL);
return 0;
}
fails if, say, this executable is not readable and suid_dumpable = 0.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | fs/proc/fd.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 0ff80f9b930f..985ea881b5bc 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c | |||
@@ -286,7 +286,7 @@ int proc_fd_permission(struct inode *inode, int mask) | |||
286 | int rv = generic_permission(inode, mask); | 286 | int rv = generic_permission(inode, mask); |
287 | if (rv == 0) | 287 | if (rv == 0) |
288 | return 0; | 288 | return 0; |
289 | if (task_pid(current) == proc_pid(inode)) | 289 | if (task_tgid(current) == proc_pid(inode)) |
290 | rv = 0; | 290 | rv = 0; |
291 | return rv; | 291 | return rv; |
292 | } | 292 | } |