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authorAmir Goldstein <amir73il@gmail.com>2020-06-21 09:37:59 +0300
committerMiklos Szeredi <mszeredi@redhat.com>2020-07-16 00:09:59 +0200
commit20396365a16dae4b4e3967fc7115d5336feb30ee (patch)
tree4de33b3229fc3e9cbb0640fb1e61e26556171b31 /fs/overlayfs/super.c
parent124c2de2c0aee96271e4ddab190083d8aa7aa71a (diff)
ovl: fix oops in ovl_indexdir_cleanup() with nfs_export=on
Mounting with nfs_export=on, xfstests overlay/031 triggers a kernel panic since v5.8-rc1 overlayfs updates. overlayfs: orphan index entry (index/00fb1..., ftype=4000, nlink=2) BUG: kernel NULL pointer dereference, address: 0000000000000030 RIP: 0010:ovl_cleanup_and_whiteout+0x28/0x220 [overlay] Bisect point at commit c21c839b8448 ("ovl: whiteout inode sharing") Minimal reproducer: -------------------------------------------------- rm -rf l u w m mkdir -p l u w m mkdir -p l/testdir touch l/testdir/testfile mount -t overlay -o lowerdir=l,upperdir=u,workdir=w,nfs_export=on overlay m echo 1 > m/testdir/testfile umount m rm -rf u/testdir mount -t overlay -o lowerdir=l,upperdir=u,workdir=w,nfs_export=on overlay m umount m -------------------------------------------------- When mount with nfs_export=on, and fail to verify an orphan index, we're cleaning this index from indexdir by calling ovl_cleanup_and_whiteout(). This dereferences ofs->workdir, that was earlier set to NULL. The design was that ovl->workdir will point at ovl->indexdir, but we are assigning ofs->indexdir to ofs->workdir only after ovl_indexdir_cleanup(). There is no reason not to do it sooner, because once we get success from ofs->indexdir = ovl_workdir_create(... there is no turning back. Reported-and-tested-by: Murphy Zhou <jencce.kernel@gmail.com> Fixes: c21c839b8448 ("ovl: whiteout inode sharing") Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs/super.c')
-rw-r--r--fs/overlayfs/super.c16
1 files changed, 7 insertions, 9 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 498d49d5dd19..31ef24dfcf88 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1354,6 +1354,12 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
if (ofs->indexdir) {
+ /* index dir will act also as workdir */
+ iput(ofs->workdir_trap);
+ ofs->workdir_trap = NULL;
+ dput(ofs->workdir);
+ ofs->workdir = dget(ofs->indexdir);
+
err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
"indexdir");
if (err)
@@ -1852,20 +1858,12 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
sb->s_flags |= SB_RDONLY;
if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
- /* index dir will act also as workdir */
- dput(ofs->workdir);
- ofs->workdir = NULL;
- iput(ofs->workdir_trap);
- ofs->workdir_trap = NULL;
-
err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
if (err)
goto out_free_oe;
/* Force r/o mount with no index dir */
- if (ofs->indexdir)
- ofs->workdir = dget(ofs->indexdir);
- else
+ if (!ofs->indexdir)
sb->s_flags |= SB_RDONLY;
}