Linux Kernel up to 7.2.9/7.3-rc5 SMB Client cifs_file_copychunk_range/cifs_remap_file_range race condition

Summaryinfo

A vulnerability categorized as very critical has been discovered in Linux Kernel up to 7.2.9/7.3-rc5. This issue affects the function cifs_file_copychunk_range/cifs_remap_file_range of the component SMB Client. Such manipulation leads to race condition. This vulnerability is listed as CVE-2026-98682. The attack may be performed from remote. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.9/7.3-rc5 and classified as very critical. Affected by this issue is the function cifs_file_copychunk_range/cifs_remap_file_range of the component SMB Client. The manipulation with an unknown input leads to a race condition vulnerability. Using CWE to declare the problem leads to CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: smb: client: drain and invalidate before server-side copy/clone cifs_file_copychunk_range() and the clone (FICLONE) path of cifs_remap_file_range() do not serialise the destination page cache against the server-side copy the way the other server-side range operations (smb3_zero_range(), smb3_punch_hole(), smb3_collapse_range() and smb3_insert_range()) do. cifs_file_copychunk_range() invalidates the destination range with filemap_invalidate_inode(), which takes and drops the mapping's invalidate_lock internally, so the lock is no longer held when the copychunk ioctl is issued. It also never drains in-flight netfs I/O on the target. The clone path never takes the invalidate_lock at all (only i_rwsem), uses a bare truncate_inode_pages_range() and likewise does not drain outstanding I/O. As a result an asynchronous destination writeback can complete after the server-side copy/clone has run and reinstate stale data over the region just written by the server, corrupting the file. This is the same class of corruption as commit d7d2adcd022b ("smb/client: flush dirty data before punching a hole") and has been seen randomly in generic/363 against Windows Server. Fix both paths to follow the established ordering: hold the target mapping's invalidate_lock across the flush and invalidation of the destination and the server ioctl, and call netfs_wait_for_outstanding_io() on the target to drain in-flight writes before the ioctl is issued. Only the target inode's invalidate_lock is required, as the source is merely flushed and not invalidated; i_rwsem (already held via lock_two_nondirectories()) is acquired before the invalidate_lock, matching the VFS lock ordering. Since filemap_invalidate_inode() takes that same lock internally, replace it with its own unmap/flush/invalidate steps instead of calling it, and return early on a zero-length copy to avoid a range underflow.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-98682 since 09/25/2026. The exploitation is known to be easy. The attack may be launched remotely. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/18/2026).

Upgrading to version 7.2.10 or 7.3-rc6 eliminates this vulnerability. Applying the patch dc71660f11ef2fecc0695a41e49cd496a9d255ab/c9b1194e8ec99d95db25db45edd2fbf690f043ab is able to eliminate this problem. 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

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.2.7
• 7.2.8
• 7.2.9
• 7.3-rc1
• 7.3-rc2
• 7.3-rc3
• 7.3-rc4
• 7.3-rc5

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

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