4.19-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 2c1cf00eeacb784781cf1c9896b8af001246d339 ]
If create_buf_file() returns an error, don't try to reference it later as a valid dentry pointer.
This problem was exposed when debugfs started to return errors instead of just NULL for some calls when they do not succeed properly.
Also, the check for WARN_ON(dentry) was just wrong :)
Reported-by: Kees Cook keescook@chromium.org Reported-and-tested-by: syzbot+16c3a70e1e9b29346c43@syzkaller.appspotmail.com Reported-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Cc: Andrew Morton akpm@linux-foundation.org Cc: David Rientjes rientjes@google.com Fixes: ff9fb72bc077 ("debugfs: return error values, not NULL") Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/relay.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/relay.c b/kernel/relay.c index 04f248644e06..9e0f52375487 100644 --- a/kernel/relay.c +++ b/kernel/relay.c @@ -428,6 +428,8 @@ static struct dentry *relay_create_buf_file(struct rchan *chan, dentry = chan->cb->create_buf_file(tmpname, chan->parent, S_IRUSR, buf, &chan->is_global); + if (IS_ERR(dentry)) + dentry = NULL;
kfree(tmpname);
@@ -461,7 +463,7 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu) dentry = chan->cb->create_buf_file(NULL, NULL, S_IRUSR, buf, &chan->is_global); - if (WARN_ON(dentry)) + if (IS_ERR_OR_NULL(dentry)) goto free_buf; }