{"id":"CVE-2026-31702","summary":"f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()\n\nIn f2fs_compress_write_end_io(), dec_page_count(sbi, type) can bring\nthe F2FS_WB_CP_DATA counter to zero, unblocking\nf2fs_wait_on_all_pages() in f2fs_put_super() on a concurrent unmount\nCPU. The unmount path then proceeds to call\nf2fs_destroy_page_array_cache(sbi), which destroys\nsbi-\u003epage_array_slab via kmem_cache_destroy(), and eventually\nkfree(sbi). Meanwhile, the bio completion callback is still executing:\nwhen it reaches page_array_free(sbi, ...), it dereferences\nsbi-\u003epage_array_slab — a destroyed slab cache — to call\nkmem_cache_free(), causing a use-after-free.\n\nThis is the same class of bug as CVE-2026-23234 (which fixed the\nequivalent race in f2fs_write_end_io() in data.c), but in the\ncompressed writeback completion path that was not covered by that fix.\n\nFix this by moving dec_page_count() to after page_array_free(), so\nthat all sbi accesses complete before the counter decrement that can\nunblock unmount. For non-last folios (where atomic_dec_return on\ncic-\u003epending_pages is nonzero), dec_page_count is called immediately\nbefore returning — page_array_free is not reached on this path, so\nthere is no post-decrement sbi access. For the last folio,\npage_array_free runs while the F2FS_WB_CP_DATA counter is still\nnonzero (this folio has not yet decremented it), keeping sbi alive,\nand dec_page_count runs as the final operation.","modified":"2026-06-18T03:54:56.561933424Z","published":"2026-05-01T13:56:01.601Z","related":["CGA-p3r2-78mm-qhc3","openSUSE-SU-2026:10793-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31702.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2c97dcb6147c8f7f25c629b93be1e69617de5d4a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/39d4ee19c1e7d753dd655aebee632271b171f43a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/57bc678f36ac03281e877c6b84877b43f964143f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c76cf339b87975ae5b2c06d2d774d5667d25a12a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ef57cd3329b40c739b9a2e1a8a21ecc4171c6280"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f5154cf3ce1c8193f0c1891d3769f62740cfe6fe"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31702.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31702"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4c8ff7095bef64fc47e996a938f7d57f9e077da3"},{"fixed":"57bc678f36ac03281e877c6b84877b43f964143f"},{"fixed":"ef57cd3329b40c739b9a2e1a8a21ecc4171c6280"},{"fixed":"f5154cf3ce1c8193f0c1891d3769f62740cfe6fe"},{"fixed":"c76cf339b87975ae5b2c06d2d774d5667d25a12a"},{"fixed":"2c97dcb6147c8f7f25c629b93be1e69617de5d4a"},{"fixed":"39d4ee19c1e7d753dd655aebee632271b171f43a"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31702.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.6.0"},{"fixed":"6.1.175"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.136"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.84"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.25"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.2"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31702.json"}}],"schema_version":"1.7.5"}