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CVE-2026-68388 is a logic flaw in the Linux kernel SMB client implementation, specifically in smb3_simple_fallocate_range(). During fallocate processing, the function queries server-reported allocated ranges so it can preserve existing file contents and zero-fill only sparse holes. If an SMB server returns an allocated range that begins before the current fallocate offset, the vulnerable code advances the current offset by the full returned range length rather than only the overlapping portion. This can cause part of a hole within the requested fallocate range to be skipped without being zero-filled, while fallocate still reports success. As a result, the file state after the operation may not match the caller's expectations. The fix changes the range-handling logic to advance only across the overlapping portion of an allocated range, ignore ranges that end before the current offset, and reject ranges whose computed end offset overflows. The correction also prevents malformed range lengths from leading to an out-of-bounds read from the zero-fill buffer.
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A Linux kernel SMB client vulnerability in smb3_simple_fallocate_range() where overlapping allocated ranges returned by the server can cause holes to be skipped during fallocate, leading to incorrect success reporting, possible later ENOSPC write failures, and prevention of an out-of-bounds zero-buffer read in malformed range cases.
A Linux kernel SMB client vulnerability involving handling of overlapping allocated ranges in fallocate.
A specific vulnerability affecting Red Hat Enterprise Linux 10.2 kernel-related packages; the content does not provide technical details beyond listing it in the advisory.
A Linux kernel vulnerability in the SMB client related to handling overlapping allocated ranges in fallocate.
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