2022-10-21 09:05:22

by Yue Hu

Subject: [PATCH] erofs: fix general protection fault when reading fragment

From: Yue Hu <[email protected]>

As syzbot reported [1], the fragment feature sb flag is not set, so
packed_inode != NULL needs to be checked in z_erofs_read_fragment().

[1] https://lore.kernel.org/all/[email protected]/

Reported-by: [email protected]
Fixes: 08a0c9ef3e7e ("erofs: support on-disk compressed fragments data")
Signed-off-by: Yue Hu <[email protected]>
---
fs/erofs/zdata.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index cce56dde135c..310f6916787a 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -659,6 +659,9 @@ static int z_erofs_read_fragment(struct inode *inode, erofs_off_t pos,
u8 *src, *dst;
unsigned int i, cnt;

+ if (!packed_inode)
+ return -EFAULT;
+
pos += EROFS_I(inode)->z_fragmentoff;
for (i = 0; i < len; i += cnt) {
cnt = min_t(unsigned int, len - i,
--
2.17.1

2022-10-21 09:10:55

by Gao Xiang

Subject: Re: [PATCH] erofs: fix general protection fault when reading fragment

On Fri, Oct 21, 2022 at 04:31:16PM +0800, Yue Hu wrote:
> From: Yue Hu <[email protected]>
>
> As syzbot reported [1], the fragment feature sb flag is not set, so
> packed_inode != NULL needs to be checked in z_erofs_read_fragment().
>
> [1] https://lore.kernel.org/all/[email protected]/
>
> Reported-by: [email protected]
> Fixes: 08a0c9ef3e7e ("erofs: support on-disk compressed fragments data")
> Signed-off-by: Yue Hu <[email protected]>
> ---
> fs/erofs/zdata.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index cce56dde135c..310f6916787a 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -659,6 +659,9 @@ static int z_erofs_read_fragment(struct inode *inode, erofs_off_t pos,
> u8 *src, *dst;
> unsigned int i, cnt;
>
> + if (!packed_inode)
> + return -EFAULT;

You should use -EFSCURRUPTED; here.

Thanks,
Gao Xiang

> +
> pos += EROFS_I(inode)->z_fragmentoff;
> for (i = 0; i < len; i += cnt) {
> cnt = min_t(unsigned int, len - i,
> --
> 2.17.1