2020-04-23 07:47:14

by Jingbo Xu

Subject: [PATCH v2] ext4: fix error pointer dereference

Don't pass error pointers to brelse().

commit 7159a986b420 ("ext4: fix some error pointer dereferences") has fixed
some cases, fix the remaining one case.

Once ext4_xattr_block_find()->ext4_sb_bread() failed, error pointer is
stored in @bs->bh, which will be passed to brelse() in the cleanup
routine of ext4_xattr_set_handle(). This will then cause a NULL panic
crash in __brelse().

BUG: unable to handle kernel NULL pointer dereference at 000000000000005b
RIP: 0010:__brelse+0x1b/0x50
Call Trace:
ext4_xattr_set_handle+0x163/0x5d0
ext4_xattr_set+0x95/0x110
__vfs_setxattr+0x6b/0x80
__vfs_setxattr_noperm+0x68/0x1b0
vfs_setxattr+0xa0/0xb0
setxattr+0x12c/0x1a0
path_setxattr+0x8d/0xc0
__x64_sys_setxattr+0x27/0x30
do_syscall_64+0x60/0x250
entry_SYSCALL_64_after_hwframe+0x49/0xbe

In this case, @bs->bh stores '-EIO' actually.

Fixes: fb265c9cb49e ("ext4: add ext4_sb_bread() to disambiguate ENOMEM cases")
Signed-off-by: Jeffle Xu <[email protected]>
Reviewed-by: Joseph Qi <[email protected]>
Cc: [email protected] # 2.6.19
---
fs/ext4/xattr.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 21df43a..01ba663 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1800,8 +1800,11 @@ struct ext4_xattr_block_find {
if (EXT4_I(inode)->i_file_acl) {
/* The inode already has an extended attribute block. */
bs->bh = ext4_sb_bread(sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
- if (IS_ERR(bs->bh))
- return PTR_ERR(bs->bh);
+ if (IS_ERR(bs->bh)) {
+ error = PTR_ERR(bs->bh);
+ bs->bh = NULL;
+ return error;
+ }
ea_bdebug(bs->bh, "b_count=%d, refcount=%d",
atomic_read(&(bs->bh->b_count)),
le32_to_cpu(BHDR(bs->bh)->h_refcount));
--
1.8.3.1

2020-04-23 08:43:46

by Ritesh Harjani

Subject: Re: [PATCH v2] ext4: fix error pointer dereference

On 4/23/20 1:16 PM, Jeffle Xu wrote:
> Don't pass error pointers to brelse().
>
> commit 7159a986b420 ("ext4: fix some error pointer dereferences") has fixed
> some cases, fix the remaining one case.
>
> Once ext4_xattr_block_find()->ext4_sb_bread() failed, error pointer is
> stored in @bs->bh, which will be passed to brelse() in the cleanup
> routine of ext4_xattr_set_handle(). This will then cause a NULL panic
> crash in __brelse().
>
> BUG: unable to handle kernel NULL pointer dereference at 000000000000005b
> RIP: 0010:__brelse+0x1b/0x50
> Call Trace:
> ext4_xattr_set_handle+0x163/0x5d0
> ext4_xattr_set+0x95/0x110
> __vfs_setxattr+0x6b/0x80
> __vfs_setxattr_noperm+0x68/0x1b0
> vfs_setxattr+0xa0/0xb0
> setxattr+0x12c/0x1a0
> path_setxattr+0x8d/0xc0
> __x64_sys_setxattr+0x27/0x30
> do_syscall_64+0x60/0x250
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> In this case, @bs->bh stores '-EIO' actually.
>
> Fixes: fb265c9cb49e ("ext4: add ext4_sb_bread() to disambiguate ENOMEM cases")
> Signed-off-by: Jeffle Xu <[email protected]>
> Reviewed-by: Joseph Qi <[email protected]>
> Cc: [email protected] # 2.6.19

Thanks for your patch. Looks good to me.
Feel free to add:

Reviewed-by: Ritesh Harjani <[email protected]>

> ---
> fs/ext4/xattr.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> index 21df43a..01ba663 100644
> --- a/fs/ext4/xattr.c
> +++ b/fs/ext4/xattr.c
> @@ -1800,8 +1800,11 @@ struct ext4_xattr_block_find {
> if (EXT4_I(inode)->i_file_acl) {
> /* The inode already has an extended attribute block. */
> bs->bh = ext4_sb_bread(sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
> - if (IS_ERR(bs->bh))
> - return PTR_ERR(bs->bh);
> + if (IS_ERR(bs->bh)) {
> + error = PTR_ERR(bs->bh);
> + bs->bh = NULL;
> + return error;
> + }
> ea_bdebug(bs->bh, "b_count=%d, refcount=%d",
> atomic_read(&(bs->bh->b_count)),
> le32_to_cpu(BHDR(bs->bh)->h_refcount));
>

2020-04-23 11:07:59

by Jan Kara

Subject: Re: [PATCH v2] ext4: fix error pointer dereference

On Thu 23-04-20 15:46:44, Jeffle Xu wrote:
> Don't pass error pointers to brelse().
>
> commit 7159a986b420 ("ext4: fix some error pointer dereferences") has fixed
> some cases, fix the remaining one case.
>
> Once ext4_xattr_block_find()->ext4_sb_bread() failed, error pointer is
> stored in @bs->bh, which will be passed to brelse() in the cleanup
> routine of ext4_xattr_set_handle(). This will then cause a NULL panic
> crash in __brelse().
>
> BUG: unable to handle kernel NULL pointer dereference at 000000000000005b
> RIP: 0010:__brelse+0x1b/0x50
> Call Trace:
> ext4_xattr_set_handle+0x163/0x5d0
> ext4_xattr_set+0x95/0x110
> __vfs_setxattr+0x6b/0x80
> __vfs_setxattr_noperm+0x68/0x1b0
> vfs_setxattr+0xa0/0xb0
> setxattr+0x12c/0x1a0
> path_setxattr+0x8d/0xc0
> __x64_sys_setxattr+0x27/0x30
> do_syscall_64+0x60/0x250
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> In this case, @bs->bh stores '-EIO' actually.
>
> Fixes: fb265c9cb49e ("ext4: add ext4_sb_bread() to disambiguate ENOMEM cases")
> Signed-off-by: Jeffle Xu <[email protected]>
> Reviewed-by: Joseph Qi <[email protected]>
> Cc: [email protected] # 2.6.19

Thanks for the patch! It looks good to me. You can add:

Reviewed-by: Jan Kara <[email protected]>

Honza

> ---
> fs/ext4/xattr.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> index 21df43a..01ba663 100644
> --- a/fs/ext4/xattr.c
> +++ b/fs/ext4/xattr.c
> @@ -1800,8 +1800,11 @@ struct ext4_xattr_block_find {
> if (EXT4_I(inode)->i_file_acl) {
> /* The inode already has an extended attribute block. */
> bs->bh = ext4_sb_bread(sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
> - if (IS_ERR(bs->bh))
> - return PTR_ERR(bs->bh);
> + if (IS_ERR(bs->bh)) {
> + error = PTR_ERR(bs->bh);
> + bs->bh = NULL;
> + return error;
> + }
> ea_bdebug(bs->bh, "b_count=%d, refcount=%d",
> atomic_read(&(bs->bh->b_count)),
> le32_to_cpu(BHDR(bs->bh)->h_refcount));
> --
> 1.8.3.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR

2020-05-14 15:00:39

by Theodore Ts'o

Subject: Re: [PATCH v2] ext4: fix error pointer dereference

On Thu, Apr 23, 2020 at 03:46:44PM +0800, Jeffle Xu wrote:
> Don't pass error pointers to brelse().
>
> commit 7159a986b420 ("ext4: fix some error pointer dereferences") has fixed
> some cases, fix the remaining one case.
>
> Once ext4_xattr_block_find()->ext4_sb_bread() failed, error pointer is
> stored in @bs->bh, which will be passed to brelse() in the cleanup
> routine of ext4_xattr_set_handle(). This will then cause a NULL panic
> crash in __brelse().
>
> BUG: unable to handle kernel NULL pointer dereference at 000000000000005b
> RIP: 0010:__brelse+0x1b/0x50
> Call Trace:
> ext4_xattr_set_handle+0x163/0x5d0
> ext4_xattr_set+0x95/0x110
> __vfs_setxattr+0x6b/0x80
> __vfs_setxattr_noperm+0x68/0x1b0
> vfs_setxattr+0xa0/0xb0
> setxattr+0x12c/0x1a0
> path_setxattr+0x8d/0xc0
> __x64_sys_setxattr+0x27/0x30
> do_syscall_64+0x60/0x250
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> In this case, @bs->bh stores '-EIO' actually.
>
> Fixes: fb265c9cb49e ("ext4: add ext4_sb_bread() to disambiguate ENOMEM cases")
> Signed-off-by: Jeffle Xu <[email protected]>
> Reviewed-by: Joseph Qi <[email protected]>
> Cc: [email protected] # 2.6.19
> Reviewed-by: Ritesh Harjani <[email protected]>
> Reviewed-by: Jan Kara <[email protected]>

Applied, thanks.

- Ted