{"id":"CVE-2026-92487","state":"PUBLISHED","title":"exfat: fix valid_size extension over a shared writable mapping","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nexfat: fix valid_size extension over a shared writable mapping\n\nWhen a shared writable mapping has its valid_size extended by a buffered\nwrite or a page fault, exfat zeroes the page-cache gap below the new\nvalid_size. A store through the mapping can race with this zeroing and be\noverwritten.\n\nFix this by zeroing the gap lazily. Drop ->map_pages so that every first\nwrite fault goes through exfat_page_mkwrite(), which advances valid_size to\ncover the faulting page. With fault-around enabled, a store could install a\nwritable PTE, skip ->page_mkwrite(), and land past valid_size without\nadvancing it. Extending valid_size one faulting page at a time also leaves\nnever-written pages in a large mapping alone.\n\nThe gap is filled with block granularity, zeroing only the not-uptodate\nblocks and preserving blocks that may hold data stored through the mapping.\nOn the buffered-write path the invalidate lock is held and the gap is\nunmapped before zeroing, so a racing store re-faults and, under the inode\nlock, completes only after the gap has been zeroed and valid_size covers\nit.","publishedAt":"2026-09-17T16:10:02.317Z","updatedAt":"2026-10-19T09:03:53.813Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"82a81a7352bcf5f2756ac33d47ee0582737e9a85","status":"affected","lessThan":"24f20986b253c3e4eb13ebe3c2007d1d352408a6","versionType":"git"},{"version":"82a81a7352bcf5f2756ac33d47ee0582737e9a85","status":"affected","lessThan":"1135704ed22f54873eb0498a232611d9eca30dd4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exfat/exfat_fs.h","fs/exfat/file.c","fs/exfat/iomap.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.2","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exfat/exfat_fs.h","fs/exfat/file.c","fs/exfat/iomap.c"]}],"references":["https://git.kernel.org/stable/c/24f20986b253c3e4eb13ebe3c2007d1d352408a6","https://git.kernel.org/stable/c/1135704ed22f54873eb0498a232611d9eca30dd4"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/92xxx/CVE-2026-92487.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-92487","state":"PUBLISHED","datePublished":"2026-09-17T16:10:02.317Z","dateUpdated":"2026-10-19T09:03:53.813Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-16T12:21:13.870Z"},"containers":{"cna":{"title":"exfat: fix valid_size extension over a shared writable mapping","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nexfat: fix valid_size extension over a shared writable mapping\n\nWhen a shared writable mapping has its valid_size extended by a buffered\nwrite or a page fault, exfat zeroes the page-cache gap below the new\nvalid_size. A store through the mapping can race with this zeroing and be\noverwritten.\n\nFix this by zeroing the gap lazily. Drop ->map_pages so that every first\nwrite fault goes through exfat_page_mkwrite(), which advances valid_size to\ncover the faulting page. With fault-around enabled, a store could install a\nwritable PTE, skip ->page_mkwrite(), and land past valid_size without\nadvancing it. Extending valid_size one faulting page at a time also leaves\nnever-written pages in a large mapping alone.\n\nThe gap is filled with block granularity, zeroing only the not-uptodate\nblocks and preserving blocks that may hold data stored through the mapping.\nOn the buffered-write path the invalidate lock is held and the gap is\nunmapped before zeroing, so a racing store re-faults and, under the inode\nlock, completes only after the gap has been zeroed and valid_size covers\nit."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"82a81a7352bcf5f2756ac33d47ee0582737e9a85","status":"affected","lessThan":"24f20986b253c3e4eb13ebe3c2007d1d352408a6","versionType":"git"},{"version":"82a81a7352bcf5f2756ac33d47ee0582737e9a85","status":"affected","lessThan":"1135704ed22f54873eb0498a232611d9eca30dd4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exfat/exfat_fs.h","fs/exfat/file.c","fs/exfat/iomap.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.2","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exfat/exfat_fs.h","fs/exfat/file.c","fs/exfat/iomap.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/24f20986b253c3e4eb13ebe3c2007d1d352408a6"},{"url":"https://git.kernel.org/stable/c/1135704ed22f54873eb0498a232611d9eca30dd4"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:03:53.813Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}