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ovl: fix wrong use of impure dir cache in ovl_iterate()

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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: 4edb83bb10 ('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>
This commit is contained in:
Amir Goldstein 2018-07-17 16:05:38 +03:00 committed by Miklos Szeredi
parent ce397d215c
commit 6781069307
1 changed files with 17 additions and 2 deletions
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19
fs/overlayfs/readdir.c
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@ -668,6 +668,21 @@ static int ovl_fill_real(struct dir_context *ctx, const char *name,
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 *file, struct dir_context *ctx)
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, struct dir_context *ctx)
*/
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);
}