CVE-2024-42256: cifs: Fix server re-repick on subrequest retry
First published: Thu Aug 08 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: cifs: Fix server re-repick on subrequest retry When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server. If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting. Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry. The problem manifests as a warning looking something like: WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30 Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux kernel | >=6.10<6.10.1 |
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Reference Links
Frequently Asked Questions
What is the severity of CVE-2024-42256?
CVE-2024-42256 is classified as a moderate severity vulnerability in the Linux kernel.
How do I fix CVE-2024-42256?
To fix CVE-2024-42256, update your Linux kernel to version 6.10.1 or later.
What impact does CVE-2024-42256 have on systems?
CVE-2024-42256 can potentially affect the reliability of file operations over CIFS, leading to improper server communication.
Is CVE-2024-42256 present in older Linux kernel versions?
Yes, CVE-2024-42256 affects Linux kernel versions between 6.10 and 6.10.1.
What components are affected by CVE-2024-42256?
CVE-2024-42256 primarily affects the CIFS component within the Linux kernel.
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