{"id":"CVE-2026-98975","title":"xfs: stop exchanging reflink flags when exchanging mappings","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfs: stop exchanging reflink flags when exchanging mappings\n\nWhen an exchange covers both files from offset 0 to i_disk_size,\nxmi_can_exchange_reflink_flags() assumes e…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < 1fa2f3a7ef7ee0f2503a4b0afe24bc8c9d0820be","Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < 7d3b9b2c9dc57f93f36c716ab752548cb4db9900","Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < 4756c94260e69ce42612b8220c3614f02f7a11d5","Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < d84d6c1a7f1e2de9e601703a326a4c1b7b421943","Linux 4.9"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:19:48.379Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98975","references":[{"url":"https://git.kernel.org/stable/c/1fa2f3a7ef7ee0f2503a4b0afe24bc8c9d0820be"},{"url":"https://git.kernel.org/stable/c/7d3b9b2c9dc57f93f36c716ab752548cb4db9900"},{"url":"https://git.kernel.org/stable/c/4756c94260e69ce42612b8220c3614f02f7a11d5"},{"url":"https://git.kernel.org/stable/c/d84d6c1a7f1e2de9e601703a326a4c1b7b421943"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.550Z","slug":"CVE-2026-98975","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nxfs: stop exchanging reflink flags when exchanging mappings\n\nWhen an exchange covers both files from offset 0 to i_disk_size,\nxmi_can_exchange_reflink_flags() assumes every mapping moved and hands\nthe reflink flag over to the other file.\n\nThat assumption is wrong.  A file can still own shared blocks past\ni_disk_size, e.g. after EXCHANGE_RANGE_TO_EOF sets a smaller size\nwithout unmapping anything.  The flag is cleared anyway, and the next\nwrite to such a block happens in place instead of CoW, corrupting the\nother file that shares it.\n\nCommit a23eca88448e (\"xfs: fix exchange-range reflink flag clearing\nissue with INO1_WRITTEN\") fixed one instance of this.  Rather than add\nanother special case, stop moving the flags.\nxfs_exchmaps_ensure_reflink() already sets the flag on both inodes\nbefore the exchange, so both just keep it.\n\nNothing sets CLEAR_INO{1,2}_REFLINK anymore.  Intents logged by older\nkernels may still carry them; recovery already masks them off, so they\nstay in the log format mask and are ignored.\n\nXFS_IOC_SWAPEXT has the same problem: it moves the reflink flag from\none inode to the other along with the extents.  Just removing that is\nnot enough here: the exchange path flags both inodes up front in\nxfs_exchmaps_ensure_reflink(), but swapext has no such step, so the\ninode receiving the shared extents would be left without the flag.\nSet it on both inodes instead, and make sure both have a CoW fork,\nsince an inode with the reflink flag is expected to have one.\n\nThe flag now stays until FALLOC_FL_UNSHARE_RANGE, xfs_scrub, or a\ntruncate to zero removes it.\n\n## Affected\n\n- `Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < 1fa2f3a7ef7ee0f2503a4b0afe24bc8c9d0820be`\n- `Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < 7d3b9b2c9dc57f93f36c716ab752548cb4db9900`\n- `Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < 4756c94260e69ce42612b8220c3614f02f7a11d5`\n- `Linux >= f0bc4d134b46607967bda1205ce3226a1bd95f42 < d84d6c1a7f1e2de9e601703a326a4c1b7b421943`\n- `Linux 4.9`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}