CVE-2026-63819
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to do sanity check on f2fs_get_node_folio_ra() kernel BUG at fs/f2fs/file.c:845! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 0 PID: 5336 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:f2fs_do_truncate_blocks+0x1115/0x1140 fs/f2fs/file.c:845 Code: fc fc 90 0f 0b e8 8b 9d 9a fd 90 0f 0b e8 83 9d 9a fd 48 89 df 48 c7 c6 60 d1 1a 8c e8 54 f1 fc fc 90 0f 0b e8 6c 9d 9a fd 90 <0f> 0b e8 64 9d 9a fd 90 0f 0b 90 e9 93 fd ff ff e8 56 9d 9a fd 90 RSP: 0018:ffffc9000e4474c0 EFLAGS: 00010283 RAX: ffffffff842b1d34 RBX: 0000000000000003 RCX: 0000000000100000 RDX: ffffc9000f03a000 RSI: 0000000000035503 RDI: 0000000000035504 RBP: ffffc9000e447608 R08: ffff8880123b0000 R09: 0000000000000002 R10: 00000000fffffffe R11: 0000000000000002 R12: 0000000000000001 R13: 0000000000000000 R14: 1ffff92001c88ea0 R15: 00000000ffff039c FS: 00007f7e02ee36c0(0000) GS:ffff88808c887000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ff0305c4000 CR3: 0000000012d4c000 CR4: 0000000000352ef0 Call Trace: <TASK> f2fs_truncate_blocks+0x10a/0x300 fs/f2fs/file.c:882 f2fs_truncate+0x471/0x7c0 fs/f2fs/file.c:940 f2fs_evict_inode+0xa3f/0x1ac0 fs/f2fs/inode.c:907 evict+0x61e/0xb10 fs/inode.c:841 f2fs_fill_super+0x5f43/0x78f0 fs/f2fs/super.c:5224 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694 vfs_get_tree+0x92/0x2a0 fs/super.c:1754 fc_mount fs/namespace.c:1193 [inline] do_new_mount_fc fs/namespace.c:3758 [inline] do_new_mount+0x341/0xd30 fs/namespace.c:3834 do_mount fs/namespace.c:4167 [inline] __do_sys_mount fs/namespace.c:4383 [inline] __se_sys_mount+0x31d/0x420 fs/namespace.c:4360 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f count = ADDRS_PER_PAGE(dn.node_folio, inode); count -= dn.ofs_in_node; f2fs_bug_on(sbi, count < 0); The fuzz test will trigger above bug_on in f2fs. The root cause should be: in the corrupted inode, there is a direct node which has the same ino and nid in its footer, so in f2fs_do_truncate_blocks(), after f2fs_get_dnode_of_data() finds such dnode: 1) ADDRS_PER_PAGE(dn.node_folio, inode) will return 923 2) once dn.ofs_in_node points to addr[923, 1017] Then it will trigger the system panic. Let's introduce NODE_TYPE_NON_IXNODE to indicate current node should not be an inode or xattr node, and then use it in below path to detect inconsistent node chain in inode mapping table: - f2fs_do_truncate_blocks - f2fs_get_dnode_of_data - f2fs_get_node_folio_ra - __get_node_folio - f2fs_sanity_check_node_footer - case NODE_TYPE_NON_IXNODE -> check whether it is inode|xnode
Executive briefing
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Evidence confidence: Not assessed Evidence-derived, not an exploitability verdict
Severity & attack characteristics
CVSS vector:CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
No CVSS vector is currently available in the source record.
Technical explanation & impact
Technical root-cause details are not available in the current source record.
Assess the impact using the published CVSS metrics and the affected vendor component.
Affected products and versions
NVD has not supplied machine-readable vulnerable CPE product/version entries for this CVE. This is an information gap, not proof that no products are affected. Check the vendor advisory references below.
Remediation & validation
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- Review the linked vendor security advisory or patch notes. Upgrade to a vendor-confirmed fixed release; do not infer a fixed version from the CVE description.
- Until patched, consider restricting network access or disabling the affected feature where operationally safe. These are temporary controls, not a substitute for a vendor fix.
- Validate the remediation with a version check and vulnerability rescan, then retain change evidence.
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