[PATCH 1/2] security: Handle dentries without inode in security_path_post_mknod()

[Roberto Sassu]

On 3/29/2024 4:05 PM, Mimi Zohar wrote:
> On Fri, 2024-03-29 at 11:56 +0100, Roberto Sassu wrote:
>> From: Roberto Sassu <roberto.sassu at huawei.com>
>>
>> Commit 08abce60d63fi ("security: Introduce path_post_mknod hook")
>> introduced security_path_post_mknod(), to replace the IMA-specific call to
>> ima_post_path_mknod().
>>
>> For symmetry with security_path_mknod(), security_path_post_mknod() is
>> called after a successful mknod operation, for any file type, rather than
>> only for regular files at the time there was the IMA call.
>>
>> However, as reported by VFS maintainers, successful mknod operation does
>> not mean that the dentry always has an inode attached to it (for example,
>> not for FIFOs on a SAMBA mount).
>>
>> If that condition happens, the kernel crashes when
>> security_path_post_mknod() attempts to verify if the inode associated to
>> the dentry is private.
>>
>> Add an extra check to first verify if there is an inode attached to the
>> dentry, before checking if the inode is private. Also add the same check to
>> the current users of the path_post_mknod hook, ima_post_path_mknod() and
>> evm_post_path_mknod().
>>
>> Finally, use the proper helper, d_backing_inode(), to retrieve the inode
>> from the dentry in ima_post_path_mknod().
>>
>> Cc: stable at vger.kernel.org # 6.8.x
> 
> Huh?  It doesn't need to be backported.

Ehm, sorry. To be removed.

>> Reported-by: Steve French <smfrench at gmail.com>
>> Closes:
>> https://lore.kernel.org/linux-kernel/CAH2r5msAVzxCUHHG8VKrMPUKQHmBpE6K9_vjhgDa1uAvwx4ppw@mail.gmail.com/
>> Fixes: 08abce60d63fi ("security: Introduce path_post_mknod hook")
> 
> -> 08abce60d63f

Ok.

Thanks

Roberto

>> Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>
> 
> Acked-by: Mimi Zohar <zohar at linux.ibm.com>
>