2017-11-04 17:22:25

by Artem Blagodarenko

[permalink] [raw]

Subject: [PATCH v2] e2fsck: Fix access after free for dx_db structure

---

dx_db structure is freed after fixing of PR_2_HTREE_BAD_ROOT
problem. Next code block use this structure to unerstand if leaf
is beeng processed.

If dx_db is freed, then root block is being processed and if_leaf
need to be set to 0.

Signed-off-by: Artem Blagodarenko <[email protected]>
---
e2fsck/pass2.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/e2fsck/pass2.c b/e2fsck/pass2.c
index 09c16179..1b0504c8 100644
--- a/e2fsck/pass2.c
+++ b/e2fsck/pass2.c
@@ -1095,7 +1095,7 @@ inline_read_fail:
fix_problem(ctx, PR_2_HTREE_BAD_ROOT, &cd->pctx)) {
clear_htree(ctx, ino);
dx_dir->numblocks = 0;
- dx_db = 0;
+ dx_db = NULL;
}
dx_dir->hashversion = root->hash_version;
if ((dx_dir->hashversion <= EXT2_HASH_TEA) &&
@@ -1107,9 +1107,10 @@ inline_read_fail:
(ext2fs_dirent_name_len(dirent) == 0) &&
(ext2fs_le16_to_cpu(limit->limit) ==
((fs->blocksize - (8 + dx_csum_size)) /
- sizeof(struct ext2_dx_entry))))
+ sizeof(struct ext2_dx_entry)))) {
dx_db->type = DX_DIRBLOCK_NODE;
- is_leaf = (dx_db->type == DX_DIRBLOCK_LEAF);
+ }
+ is_leaf = dx_db ? (dx_db->type == DX_DIRBLOCK_LEAF) : 0;
}
out_htree:

--
2.13.5 (Apple Git-94)

2017-11-06 05:50:16

by Andreas Dilger

[permalink] [raw]

Subject: Re: [PATCH v2] e2fsck: Fix access after free for dx_db structure

---

On Nov 4, 2017, at 11:22 AM, Artem Blagodarenko <[email protected]> wrote:
>
> dx_db structure is freed after fixing of PR_2_HTREE_BAD_ROOT
> problem. Next code block use this structure to unerstand if leaf
> is beeng processed.
>
> If dx_db is freed, then root block is being processed and if_leaf
> need to be set to 0.
>
> Signed-off-by: Artem Blagodarenko <[email protected]>

Reviewed-by: Andreas Dilger <[email protected]>

> ---
> e2fsck/pass2.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/e2fsck/pass2.c b/e2fsck/pass2.c
> index 09c16179..1b0504c8 100644
> --- a/e2fsck/pass2.c
> +++ b/e2fsck/pass2.c
> @@ -1095,7 +1095,7 @@ inline_read_fail:
> fix_problem(ctx, PR_2_HTREE_BAD_ROOT, &cd->pctx)) {
> clear_htree(ctx, ino);
> dx_dir->numblocks = 0;
> - dx_db = 0;
> + dx_db = NULL;
> }
> dx_dir->hashversion = root->hash_version;
> if ((dx_dir->hashversion <= EXT2_HASH_TEA) &&
> @@ -1107,9 +1107,10 @@ inline_read_fail:
> (ext2fs_dirent_name_len(dirent) == 0) &&
> (ext2fs_le16_to_cpu(limit->limit) ==
> ((fs->blocksize - (8 + dx_csum_size)) /
> - sizeof(struct ext2_dx_entry))))
> + sizeof(struct ext2_dx_entry)))) {
> dx_db->type = DX_DIRBLOCK_NODE;
> - is_leaf = (dx_db->type == DX_DIRBLOCK_LEAF);
> + }
> + is_leaf = dx_db ? (dx_db->type == DX_DIRBLOCK_LEAF) : 0;
> }
> out_htree:
>
> --
> 2.13.5 (Apple Git-94)
>


Cheers, Andreas

---

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2017-12-05 03:11:34

by Theodore Ts'o

[permalink] [raw]

Subject: Re: [PATCH v2] e2fsck: Fix access after free for dx_db structure

---

On Sun, Nov 05, 2017 at 10:49:55PM -0700, Andreas Dilger wrote:
> On Nov 4, 2017, at 11:22 AM, Artem Blagodarenko <[email protected]> wrote:
> >
> > dx_db structure is freed after fixing of PR_2_HTREE_BAD_ROOT
> > problem. Next code block use this structure to unerstand if leaf
> > is beeng processed.
> >
> > If dx_db is freed, then root block is being processed and if_leaf
> > need to be set to 0.
> >
> > Signed-off-by: Artem Blagodarenko <[email protected]>
>
> Reviewed-by: Andreas Dilger <[email protected]>

Thanks, applied.

- Ted