CVE-2022-49007

Description

From CVE.org

In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix NULL pointer dereference in nilfs_palloc_commit_free_entry() Syzbot reported a null-ptr-deref bug: NILFS (loop0): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 PID: 3603 Comm: segctord Not tainted 6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0 Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 RIP: 0010:nilfs_palloc_commit_free_entry+0xe5/0x6b0 fs/nilfs2/alloc.c:608 Code: 00 00 00 00 fc ff df 80 3c 02 00 0f 85 cd 05 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 73 08 49 8d 7e 10 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 26 05 00 00 49 8b 46 10 be a6 00 00 00 48 c7 c7 RSP: 0018:ffffc90003dff830 EFLAGS: 00010212 RAX: dffffc0000000000 RBX: ffff88802594e218 RCX: 000000000000000d RDX: 0000000000000002 RSI: 0000000000002000 RDI: 0000000000000010 RBP: ffff888071880222 R08: 0000000000000005 R09: 000000000000003f R10: 000000000000000d R11: 0000000000000000 R12: ffff888071880158 R13: ffff88802594e220 R14: 0000000000000000 R15: 0000000000000004 FS: 0000000000000000(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb1c08316a8 CR3: 0000000018560000 CR4: 0000000000350ee0 Call Trace: <TASK> nilfs_dat_commit_free fs/nilfs2/dat.c:114 [inline] nilfs_dat_commit_end+0x464/0x5f0 fs/nilfs2/dat.c:193 nilfs_dat_commit_update+0x26/0x40 fs/nilfs2/dat.c:236 nilfs_btree_commit_update_v+0x87/0x4a0 fs/nilfs2/btree.c:1940 nilfs_btree_commit_propagate_v fs/nilfs2/btree.c:2016 [inline] nilfs_btree_propagate_v fs/nilfs2/btree.c:2046 [inline] nilfs_btree_propagate+0xa00/0xd60 fs/nilfs2/btree.c:2088 nilfs_bmap_propagate+0x73/0x170 fs/nilfs2/bmap.c:337 nilfs_collect_file_data+0x45/0xd0 fs/nilfs2/segment.c:568 nilfs_segctor_apply_buffers+0x14a/0x470 fs/nilfs2/segment.c:1018 nilfs_segctor_scan_file+0x3f4/0x6f0 fs/nilfs2/segment.c:1067 nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1197 [inline] nilfs_segctor_collect fs/nilfs2/segment.c:1503 [inline] nilfs_segctor_do_construct+0x12fc/0x6af0 fs/nilfs2/segment.c:2045 nilfs_segctor_construct+0x8e3/0xb30 fs/nilfs2/segment.c:2379 nilfs_segctor_thread_construct fs/nilfs2/segment.c:2487 [inline] nilfs_segctor_thread+0x3c3/0xf30 fs/nilfs2/segment.c:2570 kthread+0x2e4/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 </TASK> ... If DAT metadata file is corrupted on disk, there is a case where req->pr_desc_bh is NULL and blocknr is 0 at nilfs_dat_commit_end() during a b-tree operation that cascadingly updates ancestor nodes of the b-tree, because nilfs_dat_commit_alloc() for a lower level block can initialize the blocknr on the same DAT entry between nilfs_dat_prepare_end() and nilfs_dat_commit_end(). If this happens, nilfs_dat_commit_end() calls nilfs_dat_commit_free() without valid buffer heads in req->pr_desc_bh and req->pr_bitmap_bh, and causes the NULL pointer dereference above in nilfs_palloc_commit_free_entry() function, which leads to a crash. Fix this by adding a NULL check on req->pr_desc_bh and req->pr_bitmap_bh before nilfs_palloc_commit_free_entry() in nilfs_dat_commit_free(). This also calls nilfs_error() in that case to notify that there is a fatal flaw in the filesystem metadata and prevent further operations.

Common Vulnerability Scoring System (CVSS) Score Details

Info alert:Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).

The following CVSS metrics and score provided are preliminary and subject to review.

CVSS v3 Score Breakdown

Red HatNVDcve.org
Base Score5.55.5N/A
Attack VectorLocalLocalN/A
Attack ComplexityLowLowN/A
Privileges RequiredLowLowN/A
User InteractionNoneNoneN/A
ScopeUnchangedUnchangedN/A
ConfidentialityNoneNoneN/A
Integrity ImpactNoneNoneN/A
Availability ImpactHighHighN/A

Vector

Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Understanding the Weakness (CWE)

CWE-476

Availability

Technical Impact: DoS: Crash, Exit, or Restart

NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.

Integrity,Confidentiality

Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory

In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.

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