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files-reg: fix error handling of rm_parent_dirs

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If unlinkat fails it means that fs is in "corrupted" state - spoiled
with non-unlinked auxiliary directories.

While on it add fixme note as this function can be racy and BUG_ON if
path contains double slashes.

Cherry-picked from Virtuozzo criu:
https://src.openvz.org/projects/OVZ/repos/criu/commits/b7b4e69fd

Changes: simplify while loop condition, remove confusing FIXME, remove
excess !count check in favour of while loop condition check

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
This commit is contained in:
Pavel Tikhomirov 2020-02-13 13:03:12 +03:00 committed by Andrei Vagin
parent 5a0943c900
commit cfed6f35e1
1 changed files with 31 additions and 16 deletions
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47
criu/files-reg.c
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@ -1792,30 +1792,42 @@ out:
return ret;
}
static void rm_parent_dirs(int mntns_root, char *path, int count)
static int rm_parent_dirs(int mntns_root, char *path, int count)
{
char *p, *prev = NULL;
int ret = -1;
if (!count)
return;
while (count > 0) {
count -= 1;
while (count-- > 0) {
p = strrchr(path, '/');
if (p)
if (p) {
/* We don't handle "//" in path */
BUG_ON(prev && (prev - p == 1));
*p = '\0';
} else {
/* Inconsistent path and count */
pr_perror("Can't strrchr \"/\" in \"%s\"/\"%s\"]"
" left count=%d\n",
path, prev ? prev + 1 : "", count + 1);
goto err;
}
if (prev)
*prev = '/';
if (unlinkat(mntns_root, path, AT_REMOVEDIR))
pr_perror("Can't remove %s AT %d", path, mntns_root);
else
pr_debug("Unlinked parent dir: %s AT %d\n", path, mntns_root);
prev = p;
if (unlinkat(mntns_root, path, AT_REMOVEDIR)) {
pr_perror("Can't remove %s AT %d", path, mntns_root);
goto err;
}
pr_debug("Unlinked parent dir: %s AT %d\n", path, mntns_root);
}
ret = 0;
err:
if (prev)
*prev = '/';
return ret;
}
/* Construct parent dir name and mkdir parent/grandparents if they're not exist */
@ -1847,6 +1859,7 @@ static int make_parent_dirs_if_need(int mntns_root, char *path)
err = mkdirat(mntns_root, path, 0777);
if (err && errno != EEXIST) {
pr_perror("Can't create dir: %s AT %d", path, mntns_root);
/* Failing anyway -> no retcode check */
rm_parent_dirs(mntns_root, path, count);
count = -1;
goto out;
@ -1933,10 +1946,11 @@ out_root:
if (linkat_hard(mntns_root, rpath, mntns_root, path, rfi->remap->uid, rfi->remap->gid, 0) < 0) {
int errno_saved = errno;
rm_parent_dirs(mntns_root, path, *level);
errno = errno_saved;
if (errno == EEXIST)
if (!rm_parent_dirs(mntns_root, path, *level) && errno_saved == EEXIST) {
errno = errno_saved;
return 1;
}
return -1;
}
@ -2124,7 +2138,8 @@ ext:
pr_perror("Failed to unlink the remap file");
goto err;
}
rm_parent_dirs(mntns_root, rfi->path, level);
if (rm_parent_dirs(mntns_root, rfi->path, level))
goto err;
}
mutex_unlock(remap_open_lock);