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| author | Amir Goldstein <amir73il@gmail.com> | 2020-06-21 09:37:59 +0300 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-07-16 00:09:59 +0200 |
| commit | 20396365a16dae4b4e3967fc7115d5336feb30ee (patch) | |
| tree | 4de33b3229fc3e9cbb0640fb1e61e26556171b31 /fs/overlayfs/super.c | |
| parent | 124c2de2c0aee96271e4ddab190083d8aa7aa71a (diff) | |
| download | linux-20396365a16dae4b4e3967fc7115d5336feb30ee.tar.bz2 | |
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.c | 16 |
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; } |