CVE-2026-89640

Summary

In the Linux kernel, the following vulnerability has been resolved:

cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0

With len == 0 (clone to EOF), the effective length is computed as:

len = src_inode->i_size - off;

If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent.

Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep().

Affected Software

VendorProductVersion RangeStatus
LinuxLinux04b38d601239b4d9be641b412cf4b7456a041c67 < b098f5e5858797827666e6cd73033f52fc39b5f6affected
LinuxLinux04b38d601239b4d9be641b412cf4b7456a041c67 < c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028affected
LinuxLinux04b38d601239b4d9be641b412cf4b7456a041c67 < b057ca17b656345d04669cb87f2aff9b31d873dbaffected
LinuxLinux04b38d601239b4d9be641b412cf4b7456a041c67 < 6c322f5cf7476ded7a9a20f7be72462065a03c68affected
LinuxLinux4.5affected
LinuxLinux0 < 4.5unaffected
LinuxLinux6.12.109 <= 6.12.*unaffected
LinuxLinux6.18.50 <= 6.18.*unaffected
LinuxLinux7.2.4 <= 7.2.*unaffected
LinuxLinux7.3-rc1 <= *unaffected

Weaknesses

References