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.
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade kernel-toolsUpgrade bpftoolUpgrade python-perfUpgrade perfUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-livepatch-5.10.162-141.675Upgrade kernelUpgrade kernel-debuginfo-common-aarch64Upgrade python-perf-debuginfoUpgrade kernel-tools-debuginfoUpgrade kernel-develUpgrade kernel-debuginfoUpgrade perf-debuginfoUpgrade kernel-livepatch-4.14.301-224.520Upgrade bpftool-debuginfoUpgrade kernel-headersUpgrade kernel-tools-devel | Mar 14, 2025 | Oct 21, 2024 |
| Debian | — | Upgrade linux | Oct 23, 2024 | Oct 23, 2024 |
| Ubuntu | — | Upgrade linux-oracle-5.15Upgrade linux-kvmUpgrade linux-aws-5.4Upgrade linux-intel-iot-realtimeUpgrade linux-gcpUpgrade linux-azure-5.15Upgrade linux-riscv-5.15Upgrade linux-intel-iotgUpgrade linux-fipsUpgrade linux-aws-fipsUpgrade linux-oracleUpgrade linux-ibmUpgrade linux-xilinx-zynqmpUpgrade linux-gcp-5.15Upgrade linux-raspiUpgrade linux-nvidia-tegra-5.15Upgrade linux-azure-fipsUpgrade linux-nvidiaUpgrade linux-aws-hweUpgrade linux-aws-5.15Upgrade linux-lowlatencyUpgrade linux-azure-fdeUpgrade linux-oracle-5.4Upgrade linux-gkeopUpgrade linux-azure-fde-5.15Upgrade linux-realtimeUpgrade linux-gkeUpgrade linux-awsUpgrade linux-gcp-5.4Upgrade linux-bluefieldUpgrade linux-hwe-5.4Upgrade linux-lowlatency-hwe-5.15Upgrade linux-hweUpgrade linux-gkeop-5.15Upgrade linux-raspi-5.4Upgrade linuxUpgrade linux-azureUpgrade linux-gcp-fipsUpgrade linux-iotUpgrade linux-intel-iotg-5.15Upgrade linux-ibm-5.4Upgrade linux-hwe-5.15Upgrade linux-azure-4.15Upgrade linux-azure-5.4Upgrade linux-gcp-4.15 | Nov 19, 2024 | Oct 21, 2024 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | May 27, 2026 | Oct 21, 2024 |
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