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authorKees Cook <keescook@chromium.org>2021-05-25 12:37:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-05-25 10:24:41 -1000
commitbfb819ea20ce8bbeeba17e1a6418bf8bda91fc28 (patch)
treed5327bdc0a2bb41db9968c7937810d40875b090a /fs
parentad9f25d338605d26acedcaf3ba5fab5ca26f1c10 (diff)
proc: Check /proc/$pid/attr/ writes against file opener
Fix another "confused deputy" weakness[1]. Writes to /proc/$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>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3851bfcdba56..58bbf334265b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2703,6 +2703,10 @@ 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) {

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