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PUBLISHED

CVE-2024-27036

cifs: Fix writeback data corruption

Reserved:2024-02-19
Published:2024-05-01
Updated:2024-05-13

Description

In the Linux kernel, the following vulnerability has been resolved: cifs: Fix writeback data corruption cifs writeback doesn't correctly handle the case where cifs_extend_writeback() hits a point where it is considering an additional folio, but this would overrun the wsize - at which point it drops out of the xarray scanning loop and calls xas_pause(). The problem is that xas_pause() advances the loop counter - thereby skipping that page. What needs to happen is for xas_reset() to be called any time we decide we don't want to process the page we're looking at, but rather send the request we are building and start a new one. Fix this by copying and adapting the netfslib writepages code as a temporary measure, with cifs writeback intending to be offloaded to netfslib in the near future. This also fixes the issue with the use of filemap_get_folios_tag() causing retry of a bunch of pages which the extender already dealt with. This can be tested by creating, say, a 64K file somewhere not on cifs (otherwise copy-offload may get underfoot), mounting a cifs share with a wsize of 64000, copying the file to it and then comparing the original file and the copy: dd if=/dev/urandom of=/tmp/64K bs=64k count=1 mount //192.168.6.1/test /mnt -o user=...,pass=...,wsize=64000 cp /tmp/64K /mnt/64K cmp /tmp/64K /mnt/64K Without the fix, the cmp fails at position 64000 (or shortly thereafter).

Product status

Default status
unaffected

d08089f649a0 before e45deec35bf7
affected

d08089f649a0 before 65f2ced69598
affected

d08089f649a0 before 844b4e132f57
affected

d08089f649a0 before f3dc1bdb6b0b
affected

Default status
affected

6.3
affected

Any version before 6.3
unaffected

6.6.23
unaffected

6.7.11
unaffected

6.8.2
unaffected

6.9
unaffected

References

https://git.kernel.org/stable/c/e45deec35bf7f1f4f992a707b2d04a8c162f2240

https://git.kernel.org/stable/c/65f2ced695982ccd516196d0a9447d85dbe2eed5

https://git.kernel.org/stable/c/844b4e132f57f1333dc79feaa035075a096762e4

https://git.kernel.org/stable/c/f3dc1bdb6b0b0693562c7c54a6c28bafa608ba3c

cve.org CVE-2024-27036

nvd.nist.gov CVE-2024-27036

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