Linux Kernel up to 6.10.0 fs/smb/client/smb2ops.c cifs_prepare_write information disclosure

Summaryinfo

A vulnerability identified as problematic has been detected in Linux Kernel up to 6.10.0. The affected element is the function cifs_prepare_write of the file fs/smb/client/smb2ops.c. This manipulation causes information disclosure. This vulnerability is handled as CVE-2024-42256. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Linux Kernel up to 6.10.0. Affected by this vulnerability is the function cifs_prepare_write of the file fs/smb/client/smb2ops.c. The manipulation with an unknown input leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2024-42256 since 07/30/2024. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

Upgrading to version 6.10.1 eliminates this vulnerability. Applying the patch b1d0a566769b/de40579b9038 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6
• 6.7
• 6.8
• 6.9
• 6.10.0

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔍
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CPE 2.2info

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• 🔍
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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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