Re: CVE-2024-36966: erofs: reliably distinguish block based and fscache mode

Re: CVE-2024-36966: erofs: reliably distinguish block based and fscache mode

[Gao Xiang]

Hi,

(+Cc Baokun Li)

On 2024/6/8 20:53, Greg Kroah-Hartman wrote:
> Description
> ===========
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> erofs: reliably distinguish block based and fscache mode
> 
> When erofs_kill_sb() is called in block dev based mode, s_bdev may not
> have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled,
> it will be mistaken for fscache mode, and then attempt to free an anon_dev
> that has never been allocated, triggering the following warning:
> 
> ============================================
> ida_free called for id=0 which is not allocated.
> WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
> Modules linked in:
> CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
> RIP: 0010:ida_free+0x134/0x140
> Call Trace:
>   <TASK>
>   erofs_kill_sb+0x81/0x90
>   deactivate_locked_super+0x35/0x80
>   get_tree_bdev+0x136/0x1e0
>   vfs_get_tree+0x2c/0xf0
>   do_new_mount+0x190/0x2f0
>   [...]
> ============================================
> 
> Now when erofs_kill_sb() is called, erofs_sb_info must have been
> initialised, so use sbi->fsid to distinguish between the two modes.
> 
> The Linux kernel CVE team has assigned CVE-2024-36966 to this issue.
> 
> 
> Affected and fixed versions
> ===========================
> 
> 	Fixed in 6.6.32 with commit f9b877a7ee31
> 	Fixed in 6.8.11 with commit dcdd49701e42
> 	Fixed in 6.9 with commit 7af2ae1b1531

For reference, this issue doesn't affect Linux kernel below 6.6.

This behavior ("s_bdev may not be initialized in erofs_kill_sb()")
is introduced due to commit aca740cecbe5 ("fs: open block device after
superblock creation").

In other words, previously .kill_sb() was called only after
fill_super failed and problematic erofs_kill_sb() called due to
setup_bdev_super() failure can only happen since Linux 6.6.

Thanks,
Gao Xiang

> 
> Please see https://www.kernel.org for a full list of currently supported
> kernel versions by the kernel community.
> 
> Unaffected versions might change over time as fixes are backported to
> older supported kernel versions.  The official CVE entry at
> 	https://cve.org/CVERecord/?id=CVE-2024-36966
> will be updated if fixes are backported, please check that for the most
> up to date information about this issue.
> 
> 
> Affected files
> ==============
> 
> The file(s) affected by this issue are:
> 	fs/erofs/super.c
> 
> 
> Mitigation
> ==========
> 
> The Linux kernel CVE team recommends that you update to the latest
> stable kernel version for this, and many other bugfixes.  Individual
> changes are never tested alone, but rather are part of a larger kernel
> release.  Cherry-picking individual commits is not recommended or
> supported by the Linux kernel community at all.  If however, updating to
> the latest release is impossible, the individual changes to resolve this
> issue can be found at these commits:
> 	https://git.kernel.org/stable/c/f9b877a7ee312ec8ce17598a7ef85cb820d7c371
> 	https://git.kernel.org/stable/c/dcdd49701e429c55b3644fd70fc58d85745f8cfe
> 	https://git.kernel.org/stable/c/7af2ae1b1531feab5d38ec9c8f472dc6cceb4606
> 

Re: CVE-2024-36966: erofs: reliably distinguish block based and fscache mode

[Baokun Li]

On 2024/6/13 17:38, Gao Xiang wrote:
> Hi,
>
> (+Cc Baokun Li)
>
> On 2024/6/8 20:53, Greg Kroah-Hartman wrote:
>> Description
>> ===========
>>
>> In the Linux kernel, the following vulnerability has been resolved:
>>
>> erofs: reliably distinguish block based and fscache mode
>>
>> When erofs_kill_sb() is called in block dev based mode, s_bdev may not
>> have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled,
>> it will be mistaken for fscache mode, and then attempt to free an 
>> anon_dev
>> that has never been allocated, triggering the following warning:
>>
>> ============================================
>> ida_free called for id=0 which is not allocated.
>> WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
>> Modules linked in:
>> CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
>> RIP: 0010:ida_free+0x134/0x140
>> Call Trace:
>>   <TASK>
>>   erofs_kill_sb+0x81/0x90
>>   deactivate_locked_super+0x35/0x80
>>   get_tree_bdev+0x136/0x1e0
>>   vfs_get_tree+0x2c/0xf0
>>   do_new_mount+0x190/0x2f0
>>   [...]
>> ============================================
>>
>> Now when erofs_kill_sb() is called, erofs_sb_info must have been
>> initialised, so use sbi->fsid to distinguish between the two modes.
>>
>> The Linux kernel CVE team has assigned CVE-2024-36966 to this issue.
>>
>>
>> Affected and fixed versions
>> ===========================
>>
>>     Fixed in 6.6.32 with commit f9b877a7ee31
>>     Fixed in 6.8.11 with commit dcdd49701e42
>>     Fixed in 6.9 with commit 7af2ae1b1531
>
> For reference, this issue doesn't affect Linux kernel below 6.6.
>
> This behavior ("s_bdev may not be initialized in erofs_kill_sb()")
> is introduced due to commit aca740cecbe5 ("fs: open block device after
> superblock creation").
>
> In other words, previously .kill_sb() was called only after
> fill_super failed and problematic erofs_kill_sb() called due to
> setup_bdev_super() failure can only happen since Linux 6.6.
>
> Thanks,
> Gao Xiang

Exactly! I'm so sorry I forgot to add the Fixes tag.


Thanks,
Baokun
>
>>
>> Please see https://www.kernel.org for a full list of currently supported
>> kernel versions by the kernel community.
>>
>> Unaffected versions might change over time as fixes are backported to
>> older supported kernel versions.  The official CVE entry at
>>     https://cve.org/CVERecord/?id=CVE-2024-36966
>> will be updated if fixes are backported, please check that for the most
>> up to date information about this issue.
>>
>>
>> Affected files
>> ==============
>>
>> The file(s) affected by this issue are:
>>     fs/erofs/super.c
>>
>>
>> Mitigation
>> ==========
>>
>> The Linux kernel CVE team recommends that you update to the latest
>> stable kernel version for this, and many other bugfixes. Individual
>> changes are never tested alone, but rather are part of a larger kernel
>> release.  Cherry-picking individual commits is not recommended or
>> supported by the Linux kernel community at all.  If however, updating to
>> the latest release is impossible, the individual changes to resolve this
>> issue can be found at these commits:
>>     https://git.kernel.org/stable/c/f9b877a7ee312ec8ce17598a7ef85cb820d7c371 
>>
>>     https://git.kernel.org/stable/c/dcdd49701e429c55b3644fd70fc58d85745f8cfe 
>>
>>     https://git.kernel.org/stable/c/7af2ae1b1531feab5d38ec9c8f472dc6cceb4606 
>>
>>

Re: CVE-2024-36966: erofs: reliably distinguish block based and fscache mode

[Greg Kroah-Hartman]

On Thu, Jun 13, 2024 at 07:21:14PM +0800, Baokun Li wrote:
> On 2024/6/13 17:38, Gao Xiang wrote:
> > Hi,
> > 
> > (+Cc Baokun Li)
> > 
> > On 2024/6/8 20:53, Greg Kroah-Hartman wrote:
> > > Description
> > > ===========
> > > 
> > > In the Linux kernel, the following vulnerability has been resolved:
> > > 
> > > erofs: reliably distinguish block based and fscache mode
> > > 
> > > When erofs_kill_sb() is called in block dev based mode, s_bdev may not
> > > have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled,
> > > it will be mistaken for fscache mode, and then attempt to free an
> > > anon_dev
> > > that has never been allocated, triggering the following warning:
> > > 
> > > ============================================
> > > ida_free called for id=0 which is not allocated.
> > > WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
> > > Modules linked in:
> > > CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
> > > RIP: 0010:ida_free+0x134/0x140
> > > Call Trace:
> > >   <TASK>
> > >   erofs_kill_sb+0x81/0x90
> > >   deactivate_locked_super+0x35/0x80
> > >   get_tree_bdev+0x136/0x1e0
> > >   vfs_get_tree+0x2c/0xf0
> > >   do_new_mount+0x190/0x2f0
> > >   [...]
> > > ============================================
> > > 
> > > Now when erofs_kill_sb() is called, erofs_sb_info must have been
> > > initialised, so use sbi->fsid to distinguish between the two modes.
> > > 
> > > The Linux kernel CVE team has assigned CVE-2024-36966 to this issue.
> > > 
> > > 
> > > Affected and fixed versions
> > > ===========================
> > > 
> > >     Fixed in 6.6.32 with commit f9b877a7ee31
> > >     Fixed in 6.8.11 with commit dcdd49701e42
> > >     Fixed in 6.9 with commit 7af2ae1b1531
> > 
> > For reference, this issue doesn't affect Linux kernel below 6.6.
> > 
> > This behavior ("s_bdev may not be initialized in erofs_kill_sb()")
> > is introduced due to commit aca740cecbe5 ("fs: open block device after
> > superblock creation").
> > 
> > In other words, previously .kill_sb() was called only after
> > fill_super failed and problematic erofs_kill_sb() called due to
> > setup_bdev_super() failure can only happen since Linux 6.6.
> > 
> > Thanks,
> > Gao Xiang
> 
> Exactly! I'm so sorry I forgot to add the Fixes tag.

No worries.  I've updated the CVE database with this information and the
json file and web site will show the new information soon when it gets
propagated.

thanks,

greg k-h

Re: CVE-2024-36966: erofs: reliably distinguish block based and fscache mode

[Baokun Li]

On 2024/6/13 21:55, Greg Kroah-Hartman wrote:
> On Thu, Jun 13, 2024 at 07:21:14PM +0800, Baokun Li wrote:
>> On 2024/6/13 17:38, Gao Xiang wrote:
>>> Hi,
>>>
>>> (+Cc Baokun Li)
>>>
>>> On 2024/6/8 20:53, Greg Kroah-Hartman wrote:
>>>> Description
>>>> ===========
>>>>
>>>> In the Linux kernel, the following vulnerability has been resolved:
>>>>
>>>> erofs: reliably distinguish block based and fscache mode
>>>>
>>>> When erofs_kill_sb() is called in block dev based mode, s_bdev may not
>>>> have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled,
>>>> it will be mistaken for fscache mode, and then attempt to free an
>>>> anon_dev
>>>> that has never been allocated, triggering the following warning:
>>>>
>>>> ============================================
>>>> ida_free called for id=0 which is not allocated.
>>>> WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
>>>> Modules linked in:
>>>> CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
>>>> RIP: 0010:ida_free+0x134/0x140
>>>> Call Trace:
>>>>    <TASK>
>>>>    erofs_kill_sb+0x81/0x90
>>>>    deactivate_locked_super+0x35/0x80
>>>>    get_tree_bdev+0x136/0x1e0
>>>>    vfs_get_tree+0x2c/0xf0
>>>>    do_new_mount+0x190/0x2f0
>>>>    [...]
>>>> ============================================
>>>>
>>>> Now when erofs_kill_sb() is called, erofs_sb_info must have been
>>>> initialised, so use sbi->fsid to distinguish between the two modes.
>>>>
>>>> The Linux kernel CVE team has assigned CVE-2024-36966 to this issue.
>>>>
>>>>
>>>> Affected and fixed versions
>>>> ===========================
>>>>
>>>>      Fixed in 6.6.32 with commit f9b877a7ee31
>>>>      Fixed in 6.8.11 with commit dcdd49701e42
>>>>      Fixed in 6.9 with commit 7af2ae1b1531
>>> For reference, this issue doesn't affect Linux kernel below 6.6.
>>>
>>> This behavior ("s_bdev may not be initialized in erofs_kill_sb()")
>>> is introduced due to commit aca740cecbe5 ("fs: open block device after
>>> superblock creation").
>>>
>>> In other words, previously .kill_sb() was called only after
>>> fill_super failed and problematic erofs_kill_sb() called due to
>>> setup_bdev_super() failure can only happen since Linux 6.6.
>>>
>>> Thanks,
>>> Gao Xiang
>> Exactly! I'm so sorry I forgot to add the Fixes tag.
> No worries.  I've updated the CVE database with this information and the
> json file and web site will show the new information soon when it gets
> propagated.
>
> thanks,
>
> greg k-h

Thank you very much for the update!

-- 
With Best Regards,
Baokun Li