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authorOleg Nesterov <oleg@redhat.com>2013-09-11 14:24:37 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 15:59:03 -0700
commit96d0df79f2644fc823f26c06491e182d87a90c2a (patch)
tree09f0d82a4ac4e0410a0067466eb04ab138db3e4f /fs/proc
parenta3c039929d01f793c47922017b6c0ae438e11598 (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>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/fd.c2
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)
int rv = generic_permission(inode, mask);
if (rv == 0)
return 0;
- if (task_pid(current) == proc_pid(inode))
+ if (task_tgid(current) == proc_pid(inode))
rv = 0;
return rv;
}