2021-05-05 13:43:33

by Anirudh Rayabharam

Subject: [PATCH] ext4: fix kernel infoleak via ext4_extent_header

Initialize eh_generation of struct ext4_extent_header to prevent leaking
info to userspace. Fixes KMSAN kernel-infoleak bug reported by syzbot at:
http://syzkaller.appspot.com/bug?id=78e9ad0e6952a3ca16e8234724b2fa92d041b9b8

Reported-by: [email protected]
Signed-off-by: Anirudh Rayabharam <[email protected]>
---
fs/ext4/extents.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 77c84d6f1af6..677d4821bcc1 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -825,6 +825,7 @@ void ext4_ext_tree_init(handle_t *handle, struct inode *inode)
eh->eh_entries = 0;
eh->eh_magic = EXT4_EXT_MAGIC;
eh->eh_max = cpu_to_le16(ext4_ext_space_root(inode, 0));
+ eh->eh_generation = 0;
ext4_mark_inode_dirty(handle, inode);
}

@@ -1090,6 +1091,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
neh->eh_magic = EXT4_EXT_MAGIC;
neh->eh_depth = 0;
+ neh->eh_generation = 0;

/* move remainder of path[depth] to the new leaf */
if (unlikely(path[depth].p_hdr->eh_entries !=
@@ -1167,6 +1169,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
neh->eh_magic = EXT4_EXT_MAGIC;
neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode, 0));
neh->eh_depth = cpu_to_le16(depth - i);
+ neh->eh_generation = 0;
fidx = EXT_FIRST_INDEX(neh);
fidx->ei_block = border;
ext4_idx_store_pblock(fidx, oldblock);
--
2.26.2

2021-05-05 16:20:26

by Eric Biggers

Subject: Re: [PATCH] ext4: fix kernel infoleak via ext4_extent_header

On Wed, May 05, 2021 at 07:00:10PM +0530, Anirudh Rayabharam wrote:
> Initialize eh_generation of struct ext4_extent_header to prevent leaking
> info to userspace. Fixes KMSAN kernel-infoleak bug reported by syzbot at:
> http://syzkaller.appspot.com/bug?id=78e9ad0e6952a3ca16e8234724b2fa92d041b9b8
>
> Reported-by: [email protected]
> Signed-off-by: Anirudh Rayabharam <[email protected]>

Can you include a "Fixes:" tag?

- Eric

2021-05-06 19:54:03

by Anirudh Rayabharam

Subject: Re: [PATCH] ext4: fix kernel infoleak via ext4_extent_header

On Wed, May 05, 2021 at 09:19:44AM -0700, Eric Biggers wrote:
> On Wed, May 05, 2021 at 07:00:10PM +0530, Anirudh Rayabharam wrote:
> > Initialize eh_generation of struct ext4_extent_header to prevent leaking
> > info to userspace. Fixes KMSAN kernel-infoleak bug reported by syzbot at:
> > http://syzkaller.appspot.com/bug?id=78e9ad0e6952a3ca16e8234724b2fa92d041b9b8
> >
> > Reported-by: [email protected]
> > Signed-off-by: Anirudh Rayabharam <[email protected]>
>
> Can you include a "Fixes:" tag?

Sent v2!

Thanks!

- Anirudh.

>
> - Eric