Commit 84889d49 authored Nov 16, 2015 by Konstantin Khlebnikov Committed by Miklos Szeredi Dec 11, 2015

ovl: check dentry positiveness in ovl_cleanup_whiteouts()



This patch fixes kernel crash at removing directory which contains
whiteouts from lower layers.

Cache of directory content passed as "list" contains entries from all
layers, including whiteouts from lower layers. So, lookup in upper dir
(moved into work at this stage) will return negative entry. Plus this
cache is filled long before and we can race with external removal.

Example:
 mkdir -p lower0/dir lower1/dir upper work overlay
 touch lower0/dir/a lower0/dir/b
 mknod lower1/dir/a c 0 0
 mount -t overlay none overlay -o lowerdir=lower1:lower0,upperdir=upper,workdir=work
 rm -fr overlay/dir

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org> # 3.18+

parent cf9a6784

fs/overlayfs/readdir.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -571,6 +571,7 @@ void ovl_cleanup_whiteouts(struct dentry upper, struct list_head list)
		(int) PTR_ERR(dentry));
		continue;
		}
		if (dentry->d_inode)
		ovl_cleanup(upper->d_inode, dentry);
		dput(dentry);
		}

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