Commit 63ce5f55 authored Feb 01, 2019 by Pan Bian Committed by Linus Torvalds Feb 01, 2019

autofs: drop dentry reference only when it is never used

autofs_expire_run() calls dput(dentry) to drop the reference count of
dentry. However, dentry is read via autofs_dentry_ino(dentry) after
that. This may result in a use-free-bug. The patch drops the reference
count of dentry only when it is never used.

Link: http://lkml.kernel.org/r/154725122396.11260.16053424107144453867.stgit@pluto-themaw-net

Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent c27d82f5

fs/autofs/expire.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -596,7 +596,6 @@ int autofs_expire_run(struct super_block *sb,
		pkt.len = dentry->d_name.len;
		memcpy(pkt.name, dentry->d_name.name, pkt.len);
		pkt.name[pkt.len] = '\0';
		dput(dentry);

		if (copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)))
		ret = -EFAULT;
		@@ -609,6 +608,8 @@ int autofs_expire_run(struct super_block *sb,
		complete_all(&ino->expire_complete);
		spin_unlock(&sbi->fs_lock);

		dput(dentry);

		return ret;
		}