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From:   Wang Shilong <wangshilong1991@gmail.com>
Date:   Fri, 19 Jun 2020 10:30:49 +0800
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Subject: Re: [PATCH v2] Valgrind reported error messages like following:
To:     Ext4 Developers List <linux-ext4@vger.kernel.org>
Cc:     ebiggers@kernel.org, Wang Shilong <wshilong@ddn.com>
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Sorry, please ignore this version, patch title is wrong...

On Fri, Jun 19, 2020 at 10:26 AM Wang Shilong <wangshilong1991@gmail.com> wrote:
>
> From: Wang Shilong <wshilong@ddn.com>
>
> ==129205==  Address 0x1b804b04 is 4 bytes after a block of size 4,096 alloc'd
> ==129205==    at 0x483980B: malloc (vg_replace_malloc.c:307)
> ==129205==    by 0x44F973: ext2fs_get_mem (ext2fs.h:1846)
> ==129205==    by 0x44F973: ext2fs_get_pathname (get_pathname.c:162)
> ==129205==    by 0x430917: print_pathname (message.c:212)
> ==129205==    by 0x430FB1: expand_percent_expression (message.c:462)
> ==129205==    by 0x430FB1: print_e2fsck_message (message.c:544)
> ==129205==    by 0x430BED: expand_at_expression (message.c:262)
> ==129205==    by 0x430BED: print_e2fsck_message (message.c:528)
> ==129205==    by 0x430450: fix_problem (problem.c:2494)
> ==129205==    by 0x423F8B: e2fsck_process_bad_inode (pass2.c:1929)
> ==129205==    by 0x425AE8: check_dir_block (pass2.c:1407)
> ==129205==    by 0x426942: check_dir_block2 (pass2.c:961)
> ==129205==    by 0x445736: ext2fs_dblist_iterate3.part.0 (dblist.c:254)
> ==129205==    by 0x423835: e2fsck_pass2 (pass2.c:187)
> ==129205==    by 0x414B19: e2fsck_run (e2fsck.c:257)
>
> Dir block might be corrupted and cause the next dirent is out
> of block size boundary, even though we have the check to avoid
> problem, memory check tools like valgrind still complains it.
>
> Patch try to fix the problem by checking if offset exceed max
> offset firstly before getting the pointer.
>
> Signed-off-by: Wang Shilong <wshilong@ddn.com>
> ---
> v1->v2:
> kept same return value for corruption case as before.
> ---
>  lib/ext2fs/csum.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
> index c2550365..417a1fba 100644
> --- a/lib/ext2fs/csum.c
> +++ b/lib/ext2fs/csum.c
> @@ -266,16 +266,14 @@ static errcode_t __get_dirent_tail(ext2_filsys fs,
>         d = dirent;
>         top = EXT2_DIRENT_TAIL(dirent, fs->blocksize);
>
> -       rec_len = translate(d->rec_len);
>         while ((void *) d < top) {
> -               if ((rec_len < 8) || (rec_len & 0x03))
> +               rec_len = translate(d->rec_len);
> +               if ((rec_len < 8) || (rec_len & 0x03) ||
> +                   (rec_len > (char *)dirent + fs->blocksize - (char *)d))
>                         return EXT2_ET_DIR_CORRUPTED;
>                 d = (struct ext2_dir_entry *)(((char *)d) + rec_len);
> -               rec_len = translate(d->rec_len);
>         }
>
> -       if ((char *)d > ((char *)dirent + fs->blocksize))
> -                       return EXT2_ET_DIR_CORRUPTED;
>         if (d != top)
>                 return EXT2_ET_DIR_NO_SPACE_FOR_CSUM;
>
> --
> 2.25.4
>