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CVE-2024-49868— btrfs: fix a NULL pointer dereference when failed to start a new trasacntion

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于btrfs文件系统在事务启动失败时会导致空指针取消引用。

AI Predicted 6.5 Difficulty: Moderate EPSS 0.29% · P20

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 3fd0a5585eb98e074fb9934549c8d85c49756c0d< 1282f001cbf56e5dd6e90a18e205a566793f4be0 affected
3fd0a5585eb98e074fb9934549c8d85c49756c0d< d73d48acf36f57362df7e4f9d76568168bf5e944 affected
3fd0a5585eb98e074fb9934549c8d85c49756c0d< 37fee9c220b92c3b7bf22b51c51dde5364e7590b affected
3fd0a5585eb98e074fb9934549c8d85c49756c0d< d13249c0df7aab885acb149695f82c54c0822a70 affected
3fd0a5585eb98e074fb9934549c8d85c49756c0d< 7ad0c5868f2f0418619089513d95230c66cb7eb4 affected
3fd0a5585eb98e074fb9934549c8d85c49756c0d< dc02c1440705e3451abd1c2c8114a5c1bb188e9f affected
3fd0a5585eb98e074fb9934549c8d85c49756c0d< 39356ec0e319ed07627b3a0f402d0608546509e6 affected
3fd0a5585eb98e074fb9934549c8d85c49756c0d< c3b47f49e83197e8dffd023ec568403bcdbb774b affected
… +10 more rows
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I. Basic Information for CVE-2024-49868

Vulnerability Information
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Vulnerability Title
btrfs: fix a NULL pointer dereference when failed to start a new trasacntion
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix a NULL pointer dereference when failed to start a new trasacntion [BUG] Syzbot reported a NULL pointer dereference with the following crash: FAULT_INJECTION: forcing a failure. start_transaction+0x830/0x1670 fs/btrfs/transaction.c:676 prepare_to_relocate+0x31f/0x4c0 fs/btrfs/relocation.c:3642 relocate_block_group+0x169/0xd20 fs/btrfs/relocation.c:3678 ... BTRFS info (device loop0): balance: ended with status: -12 Oops: general protection fault, probably for non-canonical address 0xdffffc00000000cc: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000660-0x0000000000000667] RIP: 0010:btrfs_update_reloc_root+0x362/0xa80 fs/btrfs/relocation.c:926 Call Trace: <TASK> commit_fs_roots+0x2ee/0x720 fs/btrfs/transaction.c:1496 btrfs_commit_transaction+0xfaf/0x3740 fs/btrfs/transaction.c:2430 del_balance_item fs/btrfs/volumes.c:3678 [inline] reset_balance_state+0x25e/0x3c0 fs/btrfs/volumes.c:3742 btrfs_balance+0xead/0x10c0 fs/btrfs/volumes.c:4574 btrfs_ioctl_balance+0x493/0x7c0 fs/btrfs/ioctl.c:3673 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f [CAUSE] The allocation failure happens at the start_transaction() inside prepare_to_relocate(), and during the error handling we call unset_reloc_control(), which makes fs_info->balance_ctl to be NULL. Then we continue the error path cleanup in btrfs_balance() by calling reset_balance_state() which will call del_balance_item() to fully delete the balance item in the root tree. However during the small window between set_reloc_contrl() and unset_reloc_control(), we can have a subvolume tree update and created a reloc_root for that subvolume. Then we go into the final btrfs_commit_transaction() of del_balance_item(), and into btrfs_update_reloc_root() inside commit_fs_roots(). That function checks if fs_info->reloc_ctl is in the merge_reloc_tree stage, but since fs_info->reloc_ctl is NULL, it results a NULL pointer dereference. [FIX] Just add extra check on fs_info->reloc_ctl inside btrfs_update_reloc_root(), before checking fs_info->reloc_ctl->merge_reloc_tree. That DEAD_RELOC_TREE handling is to prevent further modification to the reloc tree during merge stage, but since there is no reloc_ctl at all, we do not need to bother that.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于btrfs文件系统在事务启动失败时会导致空指针取消引用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 3fd0a5585eb98e074fb9934549c8d85c49756c0d ~ 1282f001cbf56e5dd6e90a18e205a566793f4be0 -
Linux Linux 2.6.35 -

II. Public POCs for CVE-2024-49868

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III. Intelligence Information for CVE-2024-49868

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Patches & Fixes for CVE-2024-49868 (3)

Same Patch Batch · Linux · 2024-10-21 · 372 CVEs total

CVE-2024-50043 9.8 CRITICAL nfsd: fix possible badness in FREE_STATEID
CVE-2022-48985 9.8 CRITICAL net: mana: Fix race on per-CQ variable napi work_done
CVE-2024-47695 9.8 CRITICAL RDMA/rtrs-clt: Reset cid to con_num - 1 to stay in bounds
CVE-2024-50033 9.8 CRITICAL slip: make slhc_remember() more robust against malicious packets
CVE-2024-49855 9.8 CRITICAL nbd: fix race between timeout and normal completion
CVE-2024-50047 9.8 CRITICAL smb: client: fix UAF in async decryption
CVE-2024-50046 9.8 CRITICAL NFSv4: Prevent NULL-pointer dereference in nfs42_complete_copies()
CVE-2022-49003 9.8 CRITICAL nvme: fix SRCU protection of nvme_ns_head list
CVE-2024-49996 9.4 CRITICAL cifs: Fix buffer overflow when parsing NFS reparse points
CVE-2024-47678 9.4 CRITICAL icmp: change the order of rate limits
CVE-2022-49017 8.8 HIGH tipc: re-fetch skb cb after tipc_msg_validate
CVE-2024-50029 8.8 HIGH Bluetooth: hci_conn: Fix UAF in hci_enhanced_setup_sync
CVE-2024-50041 8.8 HIGH i40e: Fix macvlan leak by synchronizing access to mac_filter_hash
CVE-2024-49939 8.8 HIGH wifi: rtw89: avoid to add interface to list twice when SER
CVE-2022-48960 8.8 HIGH net: hisilicon: Fix potential use-after-free in hix5hd2_rx()
CVE-2022-48962 8.8 HIGH net: hisilicon: Fix potential use-after-free in hisi_femac_rx()
CVE-2022-48964 8.8 HIGH ravb: Fix potential use-after-free in ravb_rx_gbeth()
CVE-2022-49015 8.8 HIGH net: hsr: Fix potential use-after-free
CVE-2022-48967 8.8 HIGH NFC: nci: Bounds check struct nfc_target arrays
CVE-2024-49930 8.8 HIGH wifi: ath11k: fix array out-of-bound access in SoC stats

Showing top 20 of 372 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2024-49868

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