| From | Kamal Mostafa <> | Subject | [PATCH 3.19.y-ckt 094/164] proc: actually make proc_fd_permission() thread-friendly | Date | Wed, 2 Dec 2015 08:59:05 -0800 |
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3.19.8-ckt11 -stable review patch. If anyone has any objections, please let me know.
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From: Oleg Nesterov <oleg@redhat.com>
commit 54708d2858e79a2bdda10bf8a20c80eb96c20613 upstream.
The commit 96d0df79f264 ("proc: make proc_fd_permission() thread-friendly") fixed the access to /proc/self/fd from sub-threads, but introduced another problem: a sub-thread can't access /proc/<tid>/fd/ or /proc/thread-self/fd if generic_permission() fails.
Change proc_fd_permission() to check same_thread_group(pid_task(), current).
Fixes: 96d0df79f264 ("proc: make proc_fd_permission() thread-friendly") Reported-by: "Jin, Yihua" <yihua.jin@intel.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- fs/proc/fd.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 8e5ad83..4b724b3 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -284,11 +284,19 @@ static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry, */ int proc_fd_permission(struct inode *inode, int mask) { - int rv = generic_permission(inode, mask); + struct task_struct *p; + int rv; + + rv = generic_permission(inode, mask); if (rv == 0) - return 0; - if (task_tgid(current) == proc_pid(inode)) + return rv; + + rcu_read_lock(); + p = pid_task(proc_pid(inode), PIDTYPE_PID); + if (p && same_thread_group(p, current)) rv = 0; + rcu_read_unlock(); + return rv; } -- 1.9.1
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