From 96d0df79f2644fc823f26c06491e182d87a90c2a Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 11 Sep 2013 14:24:37 -0700 Subject: [PATCH] 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/. Change this check to use task_tgid() so that the whole thread group can access its /proc/self/fd or /proc//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/, 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/fd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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; } -- 2.30.2