Due to a signed vs unsigned comparison, an invalid extent where
ee_block (the logical block) is so large that lblk + len overflow
wasn't getting flagged as invalid.
As a result, we tripped the BUG_ON(end < lblk) in
ext4_es_cache_extent() when trying to mount a file system with a
corrupted journal inode was corrupted.
https://bugzilla.kernel.org/show_bug.cgi?id=205197
Signed-off-by: Theodore Ts'o <[email protected]>
Cc: [email protected]
---
fs/ext4/extents.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index fb0f99dc8c22..d12bc287abdc 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -367,7 +367,7 @@ ext4_ext_max_entries(struct inode *inode, int depth)
static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
{
ext4_fsblk_t block = ext4_ext_pblock(ext);
- int len = ext4_ext_get_actual_len(ext);
+ unsigned int len = ext4_ext_get_actual_len(ext);
ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);
/*
--
2.23.0
On Tue, Oct 22, 2019 at 09:31:12PM -0400, Theodore Ts'o wrote:
> Due to a signed vs unsigned comparison, an invalid extent where
> ee_block (the logical block) is so large that lblk + len overflow
> wasn't getting flagged as invalid.
>
> As a result, we tripped the BUG_ON(end < lblk) in
> ext4_es_cache_extent() when trying to mount a file system with a
> corrupted journal inode was corrupted.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=205197
>
> Signed-off-by: Theodore Ts'o <[email protected]>
> Cc: [email protected]
> ---
> fs/ext4/extents.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index fb0f99dc8c22..d12bc287abdc 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -367,7 +367,7 @@ ext4_ext_max_entries(struct inode *inode, int depth)
> static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
> {
> ext4_fsblk_t block = ext4_ext_pblock(ext);
> - int len = ext4_ext_get_actual_len(ext);
> + unsigned int len = ext4_ext_get_actual_len(ext);
> ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);
>
> /*
> --
> 2.23.0
>
This patch can't be fixing anything because the comparison is unsigned both
before and after this patch.
- Eric
On Tue, Oct 22, 2019 at 10:44:47PM -0700, Eric Biggers wrote:
>
> This patch can't be fixing anything because the comparison is unsigned both
> before and after this patch.
Thanks, you're right; I had forgotten C's signed/unsigned rules for
addition. The funny thing is the original reporter of BZ #205197
reported that the problem went away he tried a similar patch.
- Ted
On Wed, Oct 23, 2019 at 09:15:46AM -0400, Theodore Y. Ts'o wrote:
> On Tue, Oct 22, 2019 at 10:44:47PM -0700, Eric Biggers wrote:
> >
> > This patch can't be fixing anything because the comparison is unsigned both
> > before and after this patch.
>
> Thanks, you're right; I had forgotten C's signed/unsigned rules for
> addition. The funny thing is the original reporter of BZ #205197
> reported that the problem went away he tried a similar patch.
Not trying to stick my nose in too much here but:
What does it mean if ext4_ext_get_actual_len() to return < 0?
Ira
>
> - Ted
On Wed, Oct 23, 2019 at 11:43:33AM -0700, Ira Weiny wrote:
> On Wed, Oct 23, 2019 at 09:15:46AM -0400, Theodore Y. Ts'o wrote:
> > On Tue, Oct 22, 2019 at 10:44:47PM -0700, Eric Biggers wrote:
> > >
> > > This patch can't be fixing anything because the comparison is unsigned both
> > > before and after this patch.
> >
> > Thanks, you're right; I had forgotten C's signed/unsigned rules for
> > addition. The funny thing is the original reporter of BZ #205197
> > reported that the problem went away he tried a similar patch.
>
> Not trying to stick my nose in too much here but:
>
> What does it mean if ext4_ext_get_actual_len() to return < 0?
It's not possible for it to return < 0. We probably should clean it
up to make it return an unsigned int, but that's a longer-term clean-up.
- Ted