From: yangerkun <yangerkun@huawei.com> hulk inclusion category: bugfix bugzilla: 181452, https://gitee.com/openeuler/kernel/issues/I4AI46 CVE: NA --------------------------- Or the ls for ext4 dir can run into a deadloop since info->last_pos != ctx->pos which will reset the world and start read the entry which has already got before. Details see below: 1. a dx_dir which has 3 block, block 0 as dx_root block, block 1/2 as leaf block which own the ext4_dir_entry_2 2. block 1 read ok and call_filldir which will fill the dirent and update the ctx->pos 3. block 2 read fail, but we has already fill some dirent, so we will return back to userspace will a positive return val(see ksys_getdents64) 4. the second ext4_dx_readdir will reset the world since info->last_pos != ctx->pos, and will also init the curr_hash which pos to block 1 5. So we will read block1 too, and once block2 still read fail, we can only fill one dirent because the hash of the entry in block1(besides the last one) won't greater than curr_hash 6. this time, we forget update last_pos too since the read for block2 will fail, and since we has got the one entry, ksys_getdents64 can return success 7. Latter we will trapped in a loop with step 4~6 Fix it by update last_pos too once ext4_htree_fill_tree return fail. Signed-off-by: yangerkun <yangerkun@huawei.com> Reviewed-by: Zhang Yi <yi.zhang@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- fs/ext4/dir.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c index ae520a7263395..aed33af7551ee 100644 --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -535,7 +535,7 @@ static int ext4_dx_readdir(struct file *file, struct dir_context *ctx) struct dir_private_info *info = file->private_data; struct inode *inode = file_inode(file); struct fname *fname; - int ret; + int ret = 0; if (!info) { info = ext4_htree_create_dir_info(file, ctx->pos); @@ -583,7 +583,7 @@ static int ext4_dx_readdir(struct file *file, struct dir_context *ctx) info->curr_minor_hash, &info->next_hash); if (ret < 0) - return ret; + goto finished; if (ret == 0) { ctx->pos = ext4_get_htree_eof(file); break; @@ -614,7 +614,7 @@ static int ext4_dx_readdir(struct file *file, struct dir_context *ctx) } finished: info->last_pos = ctx->pos; - return 0; + return ret < 0 ? ret : 0; } static int ext4_dir_open(struct inode * inode, struct file * filp) -- 2.25.1