4.18-stable review patch. If anyone has any objections, please let me know.
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From: Amir Goldstein amir73il@gmail.com
commit 67810693077afc1ebf9e1646af300436cb8103c2 upstream.
Only upper dir can be impure, but if we are in the middle of iterating a lower real dir, dir could be copied up and marked impure. We only want the impure cache if we started iterating a real upper dir to begin with.
Aditya Kali reported that the following reproducer hits the WARN_ON(!cache->refcount) in ovl_get_cache():
docker run --rm drupal:8.5.4-fpm-alpine \ sh -c 'cd /var/www/html/vendor/symfony && \ chown -R www-data:www-data . && ls -l .'
Reported-by: Aditya Kali adityakali@google.com Tested-by: Aditya Kali adityakali@google.com Fixes: 4edb83bb1041 ('ovl: constant d_ino for non-merge dirs') Cc: stable@vger.kernel.org # v4.14 Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/overlayfs/readdir.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
--- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -668,6 +668,21 @@ static int ovl_fill_real(struct dir_cont return orig_ctx->actor(orig_ctx, name, namelen, offset, ino, d_type); }
+static bool ovl_is_impure_dir(struct file *file) +{ + struct ovl_dir_file *od = file->private_data; + struct inode *dir = d_inode(file->f_path.dentry); + + /* + * Only upper dir can be impure, but if we are in the middle of + * iterating a lower real dir, dir could be copied up and marked + * impure. We only want the impure cache if we started iterating + * a real upper dir to begin with. + */ + return od->is_upper && ovl_test_flag(OVL_IMPURE, dir); + +} + static int ovl_iterate_real(struct file *file, struct dir_context *ctx) { int err; @@ -696,7 +711,7 @@ static int ovl_iterate_real(struct file rdt.parent_ino = stat.ino; }
- if (ovl_test_flag(OVL_IMPURE, d_inode(dir))) { + if (ovl_is_impure_dir(file)) { rdt.cache = ovl_cache_get_impure(&file->f_path); if (IS_ERR(rdt.cache)) return PTR_ERR(rdt.cache); @@ -727,7 +742,7 @@ static int ovl_iterate(struct file *file */ if (ovl_xino_bits(dentry->d_sb) || (ovl_same_sb(dentry->d_sb) && - (ovl_test_flag(OVL_IMPURE, d_inode(dentry)) || + (ovl_is_impure_dir(file) || OVL_TYPE_MERGE(ovl_path_type(dentry->d_parent))))) { return ovl_iterate_real(file, ctx); }