[v1] ext4: fix off by one issue in alloc_flex_gd()

[PATCH] ext4: fix off by one issue in alloc_flex_gd()

Posted by libaokun@huaweicloud.com 1 year, 4 months ago

From: Baokun Li <libaokun1@huawei.com>

Wesley reported an issue:

==================================================================
EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks
------------[ cut here ]------------
kernel BUG at fs/ext4/resize.c:324!
CPU: 9 UID: 0 PID: 3576 Comm: resize2fs Not tainted 6.11.0+ #27
RIP: 0010:ext4_resize_fs+0x1212/0x12d0
Call Trace:
 __ext4_ioctl+0x4e0/0x1800
 ext4_ioctl+0x12/0x20
 __x64_sys_ioctl+0x99/0xd0
 x64_sys_call+0x1206/0x20d0
 do_syscall_64+0x72/0x110
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
==================================================================

While reviewing the patch, Honza found that when adjusting resize_bg in
alloc_flex_gd(), it was possible for flex_gd->resize_bg to be bigger than
flexbg_size.

The reproduction of the problem requires the following:

 o_group = flexbg_size * 2 * n;
 o_size = (o_group + 1) * group_size;
 n_group: [o_group + flexbg_size, o_group + flexbg_size * 2)
 o_size = (n_group + 1) * group_size;

Take n=0,flexbg_size=16 as an example:

              last:15
|o---------------|--------------n-|
o_group:0    resize to      n_group:30

The corresponding reproducer is:

img=test.img
truncate -s 600M $img
mkfs.ext4 -F $img -b 1024 -G 16 8M
dev=`losetup -f --show $img`
mkdir -p /tmp/test
mount $dev /tmp/test
resize2fs $dev 248M

Delete the problematic plus 1 to fix the issue, and add a WARN_ON_ONCE()
to prevent the issue from happening again.

Reported-by: Wesley Hershberger <wesley.hershberger@canonical.com>
Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231
Reported-by: Stéphane Graber <stgraber@stgraber.org>
Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com/
Tested-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Tested-by: Eric Sandeen <sandeen@redhat.com>
Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()")
Cc: stable@vger.kernel.org
Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
 fs/ext4/resize.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index e04eb08b9060..397970121d43 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -253,9 +253,9 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,
 	/* Avoid allocating large 'groups' array if not needed */
 	last_group = o_group | (flex_gd->resize_bg - 1);
 	if (n_group <= last_group)
-		flex_gd->resize_bg = 1 << fls(n_group - o_group + 1);
+		flex_gd->resize_bg = 1 << fls(n_group - o_group);
 	else if (n_group - last_group < flex_gd->resize_bg)
-		flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1),
+		flex_gd->resize_bg = 1 << max(fls(last_group - o_group),
 					      fls(n_group - last_group));
 
 	flex_gd->groups = kmalloc_array(flex_gd->resize_bg,
-- 
2.46.0

Re: [PATCH] ext4: fix off by one issue in alloc_flex_gd()

Posted by Jan Kara 1 year, 4 months ago

On Fri 27-09-24 14:36:20, libaokun@huaweicloud.com wrote:
> From: Baokun Li <libaokun1@huawei.com>
> 
> Wesley reported an issue:
> 
> ==================================================================
> EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks
> ------------[ cut here ]------------
> kernel BUG at fs/ext4/resize.c:324!
> CPU: 9 UID: 0 PID: 3576 Comm: resize2fs Not tainted 6.11.0+ #27
> RIP: 0010:ext4_resize_fs+0x1212/0x12d0
> Call Trace:
>  __ext4_ioctl+0x4e0/0x1800
>  ext4_ioctl+0x12/0x20
>  __x64_sys_ioctl+0x99/0xd0
>  x64_sys_call+0x1206/0x20d0
>  do_syscall_64+0x72/0x110
>  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> ==================================================================
> 
> While reviewing the patch, Honza found that when adjusting resize_bg in
> alloc_flex_gd(), it was possible for flex_gd->resize_bg to be bigger than
> flexbg_size.
> 
> The reproduction of the problem requires the following:
> 
>  o_group = flexbg_size * 2 * n;
>  o_size = (o_group + 1) * group_size;
>  n_group: [o_group + flexbg_size, o_group + flexbg_size * 2)
>  o_size = (n_group + 1) * group_size;
> 
> Take n=0,flexbg_size=16 as an example:
> 
>               last:15
> |o---------------|--------------n-|
> o_group:0    resize to      n_group:30
> 
> The corresponding reproducer is:
> 
> img=test.img
> truncate -s 600M $img
> mkfs.ext4 -F $img -b 1024 -G 16 8M
> dev=`losetup -f --show $img`
> mkdir -p /tmp/test
> mount $dev /tmp/test
> resize2fs $dev 248M
> 
> Delete the problematic plus 1 to fix the issue, and add a WARN_ON_ONCE()
> to prevent the issue from happening again.

I don't think you are adding WARN_ON_ONCE() :). Otherwise feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> 
> Reported-by: Wesley Hershberger <wesley.hershberger@canonical.com>
> Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231
> Reported-by: Stéphane Graber <stgraber@stgraber.org>
> Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com/
> Tested-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
> Tested-by: Eric Sandeen <sandeen@redhat.com>
> Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> ---
>  fs/ext4/resize.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index e04eb08b9060..397970121d43 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -253,9 +253,9 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,
>  	/* Avoid allocating large 'groups' array if not needed */
>  	last_group = o_group | (flex_gd->resize_bg - 1);
>  	if (n_group <= last_group)
> -		flex_gd->resize_bg = 1 << fls(n_group - o_group + 1);
> +		flex_gd->resize_bg = 1 << fls(n_group - o_group);
>  	else if (n_group - last_group < flex_gd->resize_bg)
> -		flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1),
> +		flex_gd->resize_bg = 1 << max(fls(last_group - o_group),
>  					      fls(n_group - last_group));
>  
>  	flex_gd->groups = kmalloc_array(flex_gd->resize_bg,
> -- 
> 2.46.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext4: fix off by one issue in alloc_flex_gd()

Posted by Baokun Li 1 year, 4 months ago

On 2024/9/27 18:56, Jan Kara wrote:
> On Fri 27-09-24 14:36:20, libaokun@huaweicloud.com wrote:
>> From: Baokun Li <libaokun1@huawei.com>
>>
>> Wesley reported an issue:
>>
>> ==================================================================
>> EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks
>> ------------[ cut here ]------------
>> kernel BUG at fs/ext4/resize.c:324!
>> CPU: 9 UID: 0 PID: 3576 Comm: resize2fs Not tainted 6.11.0+ #27
>> RIP: 0010:ext4_resize_fs+0x1212/0x12d0
>> Call Trace:
>>   __ext4_ioctl+0x4e0/0x1800
>>   ext4_ioctl+0x12/0x20
>>   __x64_sys_ioctl+0x99/0xd0
>>   x64_sys_call+0x1206/0x20d0
>>   do_syscall_64+0x72/0x110
>>   entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> ==================================================================
>>
>> While reviewing the patch, Honza found that when adjusting resize_bg in
>> alloc_flex_gd(), it was possible for flex_gd->resize_bg to be bigger than
>> flexbg_size.
>>
>> The reproduction of the problem requires the following:
>>
>>   o_group = flexbg_size * 2 * n;
>>   o_size = (o_group + 1) * group_size;
>>   n_group: [o_group + flexbg_size, o_group + flexbg_size * 2)
>>   o_size = (n_group + 1) * group_size;
>>
>> Take n=0,flexbg_size=16 as an example:
>>
>>                last:15
>> |o---------------|--------------n-|
>> o_group:0    resize to      n_group:30
>>
>> The corresponding reproducer is:
>>
>> img=test.img
>> truncate -s 600M $img
>> mkfs.ext4 -F $img -b 1024 -G 16 8M
>> dev=`losetup -f --show $img`
>> mkdir -p /tmp/test
>> mount $dev /tmp/test
>> resize2fs $dev 248M
>>
>> Delete the problematic plus 1 to fix the issue, and add a WARN_ON_ONCE()
>> to prevent the issue from happening again.
> I don't think you are adding WARN_ON_ONCE() :). Otherwise feel free to add:
>
> Reviewed-by: Jan Kara <jack@suse.cz>
>
> 								Honza

Oh no, I forgot to add the added modifications! 😅

Thank you for your review!

I will send out v2. soon.


Thanks,
Baokun
>> Reported-by: Wesley Hershberger <wesley.hershberger@canonical.com>
>> Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231
>> Reported-by: Stéphane Graber <stgraber@stgraber.org>
>> Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com/
>> Tested-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
>> Tested-by: Eric Sandeen <sandeen@redhat.com>
>> Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Baokun Li <libaokun1@huawei.com>
>> ---
>>   fs/ext4/resize.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
>> index e04eb08b9060..397970121d43 100644
>> --- a/fs/ext4/resize.c
>> +++ b/fs/ext4/resize.c
>> @@ -253,9 +253,9 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,
>>   	/* Avoid allocating large 'groups' array if not needed */
>>   	last_group = o_group | (flex_gd->resize_bg - 1);
>>   	if (n_group <= last_group)
>> -		flex_gd->resize_bg = 1 << fls(n_group - o_group + 1);
>> +		flex_gd->resize_bg = 1 << fls(n_group - o_group);
>>   	else if (n_group - last_group < flex_gd->resize_bg)
>> -		flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1),
>> +		flex_gd->resize_bg = 1 << max(fls(last_group - o_group),
>>   					      fls(n_group - last_group));
>>   
>>   	flex_gd->groups = kmalloc_array(flex_gd->resize_bg,
>> -- 
>> 2.46.0
>>
-- 
With Best Regards,
Baokun Li

Re: [PATCH] ext4: fix off by one issue in alloc_flex_gd()

Posted by Aleksandr Mikhalitsyn 1 year, 4 months ago

On Fri, Sep 27, 2024 at 8:39 AM <libaokun@huaweicloud.com> wrote:
>
> From: Baokun Li <libaokun1@huawei.com>
>
> Wesley reported an issue:
>
> ==================================================================
> EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks
> ------------[ cut here ]------------
> kernel BUG at fs/ext4/resize.c:324!
> CPU: 9 UID: 0 PID: 3576 Comm: resize2fs Not tainted 6.11.0+ #27
> RIP: 0010:ext4_resize_fs+0x1212/0x12d0
> Call Trace:
>  __ext4_ioctl+0x4e0/0x1800
>  ext4_ioctl+0x12/0x20
>  __x64_sys_ioctl+0x99/0xd0
>  x64_sys_call+0x1206/0x20d0
>  do_syscall_64+0x72/0x110
>  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> ==================================================================
>
> While reviewing the patch, Honza found that when adjusting resize_bg in
> alloc_flex_gd(), it was possible for flex_gd->resize_bg to be bigger than
> flexbg_size.
>
> The reproduction of the problem requires the following:
>
>  o_group = flexbg_size * 2 * n;
>  o_size = (o_group + 1) * group_size;
>  n_group: [o_group + flexbg_size, o_group + flexbg_size * 2)
>  o_size = (n_group + 1) * group_size;
>
> Take n=0,flexbg_size=16 as an example:
>
>               last:15
> |o---------------|--------------n-|
> o_group:0    resize to      n_group:30
>
> The corresponding reproducer is:
>
> img=test.img
> truncate -s 600M $img
> mkfs.ext4 -F $img -b 1024 -G 16 8M
> dev=`losetup -f --show $img`
> mkdir -p /tmp/test
> mount $dev /tmp/test
> resize2fs $dev 248M
>
> Delete the problematic plus 1 to fix the issue, and add a WARN_ON_ONCE()
> to prevent the issue from happening again.
>
> Reported-by: Wesley Hershberger <wesley.hershberger@canonical.com>
> Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231
> Reported-by: Stéphane Graber <stgraber@stgraber.org>
> Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com/
> Tested-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
> Tested-by: Eric Sandeen <sandeen@redhat.com>
> Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Baokun Li <libaokun1@huawei.com>

Thanks, Baokun!

JFYI, I'm on the way to submit a test to xfstests suite.

Kind regards,
Alex

> ---
>  fs/ext4/resize.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index e04eb08b9060..397970121d43 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -253,9 +253,9 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,
>         /* Avoid allocating large 'groups' array if not needed */
>         last_group = o_group | (flex_gd->resize_bg - 1);
>         if (n_group <= last_group)
> -               flex_gd->resize_bg = 1 << fls(n_group - o_group + 1);
> +               flex_gd->resize_bg = 1 << fls(n_group - o_group);
>         else if (n_group - last_group < flex_gd->resize_bg)
> -               flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1),
> +               flex_gd->resize_bg = 1 << max(fls(last_group - o_group),
>                                               fls(n_group - last_group));
>
>         flex_gd->groups = kmalloc_array(flex_gd->resize_bg,
> --
> 2.46.0
>

Re: [PATCH] ext4: fix off by one issue in alloc_flex_gd()

Posted by Baokun Li 1 year, 4 months ago

On 2024/9/27 16:22, Aleksandr Mikhalitsyn wrote:
> On Fri, Sep 27, 2024 at 8:39 AM <libaokun@huaweicloud.com> wrote:
>> From: Baokun Li <libaokun1@huawei.com>
>>
>> Wesley reported an issue:
>>
>> ==================================================================
>> EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks
>> ------------[ cut here ]------------
>> kernel BUG at fs/ext4/resize.c:324!
>> CPU: 9 UID: 0 PID: 3576 Comm: resize2fs Not tainted 6.11.0+ #27
>> RIP: 0010:ext4_resize_fs+0x1212/0x12d0
>> Call Trace:
>>   __ext4_ioctl+0x4e0/0x1800
>>   ext4_ioctl+0x12/0x20
>>   __x64_sys_ioctl+0x99/0xd0
>>   x64_sys_call+0x1206/0x20d0
>>   do_syscall_64+0x72/0x110
>>   entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> ==================================================================
>>
>> While reviewing the patch, Honza found that when adjusting resize_bg in
>> alloc_flex_gd(), it was possible for flex_gd->resize_bg to be bigger than
>> flexbg_size.
>>
>> The reproduction of the problem requires the following:
>>
>>   o_group = flexbg_size * 2 * n;
>>   o_size = (o_group + 1) * group_size;
>>   n_group: [o_group + flexbg_size, o_group + flexbg_size * 2)
>>   o_size = (n_group + 1) * group_size;
>>
>> Take n=0,flexbg_size=16 as an example:
>>
>>                last:15
>> |o---------------|--------------n-|
>> o_group:0    resize to      n_group:30
>>
>> The corresponding reproducer is:
>>
>> img=test.img
>> truncate -s 600M $img
>> mkfs.ext4 -F $img -b 1024 -G 16 8M
>> dev=`losetup -f --show $img`
>> mkdir -p /tmp/test
>> mount $dev /tmp/test
>> resize2fs $dev 248M
>>
>> Delete the problematic plus 1 to fix the issue, and add a WARN_ON_ONCE()
>> to prevent the issue from happening again.
>>
>> Reported-by: Wesley Hershberger <wesley.hershberger@canonical.com>
>> Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2081231
>> Reported-by: Stéphane Graber <stgraber@stgraber.org>
>> Closes: https://lore.kernel.org/all/20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com/
>> Tested-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
>> Tested-by: Eric Sandeen <sandeen@redhat.com>
>> Fixes: 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation in alloc_flex_gd()")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> Thanks, Baokun!
>
> JFYI, I'm on the way to submit a test to xfstests suite.
>
> Kind regards,
> Alex
Okay. Thanks for doing this.

Cheers,
Baokun
>> ---
>>   fs/ext4/resize.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
>> index e04eb08b9060..397970121d43 100644
>> --- a/fs/ext4/resize.c
>> +++ b/fs/ext4/resize.c
>> @@ -253,9 +253,9 @@ static struct ext4_new_flex_group_data *alloc_flex_gd(unsigned int flexbg_size,
>>          /* Avoid allocating large 'groups' array if not needed */
>>          last_group = o_group | (flex_gd->resize_bg - 1);
>>          if (n_group <= last_group)
>> -               flex_gd->resize_bg = 1 << fls(n_group - o_group + 1);
>> +               flex_gd->resize_bg = 1 << fls(n_group - o_group);
>>          else if (n_group - last_group < flex_gd->resize_bg)
>> -               flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1),
>> +               flex_gd->resize_bg = 1 << max(fls(last_group - o_group),
>>                                                fls(n_group - last_group));
>>
>>          flex_gd->groups = kmalloc_array(flex_gd->resize_bg,
>> --
>> 2.46.0
>>

-- 
With Best Regards,
Baokun Li