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| author | Kees Cook <keescook@chromium.org> | 2021-05-25 12:37:35 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-06-03 09:00:28 +0200 |
| commit | fb003a1bd60358c0ccee0145079de258a6cf0ba8 (patch) | |
| tree | 836477bed1238c9c4a24beda3feb769fd4f59c0d | |
| parent | 03b777ce8d7030f7b9d69c77eb706cf6b134655c (diff) | |
| download | linux-stable-fb003a1bd60358c0ccee0145079de258a6cf0ba8.tar.gz linux-stable-fb003a1bd60358c0ccee0145079de258a6cf0ba8.tar.bz2 linux-stable-fb003a1bd60358c0ccee0145079de258a6cf0ba8.zip | |
proc: Check /proc/$pid/attr/ writes against file opener
commit bfb819ea20ce8bbeeba17e1a6418bf8bda91fc28 upstream.
Fix another "confused deputy" weakness[1]. Writes to /proc/$pid/attr/
files need to check the opener credentials, since these fds do not
transition state across execve(). Without this, it is possible to
trick another process (which may have different credentials) to write
to its own /proc/$pid/attr/ files, leading to unexpected and possibly
exploitable behaviors.
[1] https://www.kernel.org/doc/html/latest/security/credentials.html?highlight=confused#open-file-credentials
Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/proc/base.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index 55ce0ee9c5c7..297ea12b3cfd 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2704,6 +2704,10 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf, void *page; int rv; + /* A task may only write when it was the opener. */ + if (file->f_cred != current_real_cred()) + return -EPERM; + rcu_read_lock(); task = pid_task(proc_pid(inode), PIDTYPE_PID); if (!task) { |