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| author | yangerkun <yangerkun@huawei.com> | 2021-09-14 19:14:15 +0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2021-10-01 00:05:09 -0400 |
| commit | 42cb447410d024e9d54139ae9c21ea132a8c384c (patch) | |
| tree | eec6be15b2eabb5b26e87f27ef9fb629965d113d /fs/ext4 | |
| parent | bb9464e08309f6befe80866f5be51778ca355ee9 (diff) | |
| download | linux-42cb447410d024e9d54139ae9c21ea132a8c384c.tar.bz2 | |
ext4: fix potential infinite loop in ext4_dx_readdir()
When ext4_htree_fill_tree() fails, ext4_dx_readdir() can run into an
infinite loop since if info->last_pos != ctx->pos this will reset the
directory scan and reread the failing entry. For example:
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
Cc: stable@kernel.org
Signed-off-by: yangerkun <yangerkun@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20210914111415.3921954-1-yangerkun@huawei.com
Diffstat (limited to 'fs/ext4')
| -rw-r--r-- | fs/ext4/dir.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c index ffb295aa891c..74b172a4adda 100644 --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -551,7 +551,7 @@ 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); @@ -599,7 +599,7 @@ 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; @@ -630,7 +630,7 @@ 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_release_dir(struct inode *inode, struct file *filp) |