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autofs: drop dentry reference only when it is never used

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[ Upstream commit 63ce5f552beb9bdb41546b3a26c4374758b21815 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Pan Bian 2019-02-01 14:21:26 -08:00 committed by Greg Kroah-Hartman
parent c3ce520779
commit 07f67e6e9a
1 changed files with 2 additions and 1 deletions
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3
fs/autofs4/expire.c
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@ -563,7 +563,6 @@ int autofs4_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;
@ -576,6 +575,8 @@ int autofs4_expire_run(struct super_block *sb,
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
dput(dentry);
return ret;
}