CVE-2021-46989— hfsplus: prevent corruption in shrinking truncate
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，该漏洞源于如果目录文件中的第一个盘区记录已满，则会从盘区溢出文件中分配新的记录。
Affected Version Matrix 14
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | 31651c607151f1034cfb57e5a78678bea54c362b< 52dde855663e5db824af51db39b5757d2ef3e28a |
affected |
31651c607151f1034cfb57e5a78678bea54c362b< c451a6bafb5f422197d31536f82116aed132b72c |
affected | ||
31651c607151f1034cfb57e5a78678bea54c362b< adbd8a2a8cc05d9e501f93e5c95c59307874cc99 |
affected | ||
31651c607151f1034cfb57e5a78678bea54c362b< c477f62db1a0c0ecaa60a29713006ceeeb04b685 |
affected | ||
31651c607151f1034cfb57e5a78678bea54c362b< 97314e45aa1223a42d60256a62c5d9af54baf446 |
affected | ||
31651c607151f1034cfb57e5a78678bea54c362b< c3187cf32216313fb316084efac4dab3a8459b1d |
affected | ||
4.19 |
affected | ||
< 4.19 |
unaffected | ||
| … +6 more rows | |||
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I. Basic Information for CVE-2021-46989
Vulnerability Information
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Vulnerability Title
hfsplus: prevent corruption in shrinking truncate
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: prevent corruption in shrinking truncate
I believe there are some issues introduced by commit 31651c607151
("hfsplus: avoid deadlock on file truncation")
HFS+ has extent records which always contains 8 extents. In case the
first extent record in catalog file gets full, new ones are allocated from
extents overflow file.
In case shrinking truncate happens to middle of an extent record which
locates in extents overflow file, the logic in hfsplus_file_truncate() was
changed so that call to hfs_brec_remove() is not guarded any more.
Right action would be just freeing the extents that exceed the new size
inside extent record by calling hfsplus_free_extents(), and then check if
the whole extent record should be removed. However since the guard
(blk_cnt > start) is now after the call to hfs_brec_remove(), this has
unfortunate effect that the last matching extent record is removed
unconditionally.
To reproduce this issue, create a file which has at least 10 extents, and
then perform shrinking truncate into middle of the last extent record, so
that the number of remaining extents is not under or divisible by 8. This
causes the last extent record (8 extents) to be removed totally instead of
truncating into middle of it. Thus this causes corruption, and lost data.
Fix for this is simply checking if the new truncated end is below the
start of this extent record, making it safe to remove the full extent
record. However call to hfs_brec_remove() can't be moved to it's previous
place since we're dropping ->tree_lock and it can cause a race condition
and the cached info being invalidated possibly corrupting the node data.
Another issue is related to this one. When entering into the block
(blk_cnt > start) we are not holding the ->tree_lock. We break out from
the loop not holding the lock, but hfs_find_exit() does unlock it. Not
sure if it's possible for someone else to take the lock under our feet,
but it can cause hard to debug errors and premature unlocking. Even if
there's no real risk of it, the locking should still always be kept in
balance. Thus taking the lock now just before the check.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
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，该漏洞源于如果目录文件中的第一个盘区记录已满，则会从盘区溢出文件中分配新的记录。
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
II. Public POCs for CVE-2021-46989
| # | POC Description | Source Link | Shenlong Link |
|---|
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Other References for CVE-2021-46989 (4)
Same Patch Batch · Linux · 2024-02-28 · 86 CVEs total
| CVE-2021-47013 | 9.8 CRITICAL | net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send |
| CVE-2021-47036 | 9.8 CRITICAL | udp: skip L4 aggregation for UDP tunnel packets |
| CVE-2021-46999 | 9.8 CRITICAL | sctp: do asoc update earlier in sctp_sf_do_dupcook_a |
| CVE-2021-47035 | 8.8 HIGH | iommu/vt-d: Remove WO permissions on second-level paging entries |
| CVE-2021-47017 | 8.8 HIGH | ath10k: Fix a use after free in ath10k_htc_send_bundle |
| CVE-2021-47049 | 8.4 HIGH | Drivers: hv: vmbus: Use after free in __vmbus_open() |
| CVE-2021-47014 | 7.8 HIGH | net/sched: act_ct: fix wild memory access when clearing fragments |
| CVE-2020-36785 | 7.8 HIGH | media: atomisp: Fix use after free in atomisp_alloc_css_stat_bufs() |
| CVE-2021-47040 | 7.8 HIGH | io_uring: fix overflows checks in provide buffers |
| CVE-2021-47048 | 7.8 HIGH | spi: spi-zynqmp-gqspi: fix use-after-free in zynqmp_qspi_exec_op |
| CVE-2021-46984 | 7.8 HIGH | kyber: fix out of bounds access when preempted |
| CVE-2021-46993 | 7.8 HIGH | sched: Fix out-of-bound access in uclamp |
| CVE-2021-46998 | 7.8 HIGH | ethernet:enic: Fix a use after free bug in enic_hard_start_xmit |
| CVE-2021-46992 | 7.8 HIGH | netfilter: nftables: avoid overflows in nft_hash_buckets() |
| CVE-2021-46977 | 7.8 HIGH | KVM: VMX: Disable preemption when probing user return MSRs |
| CVE-2021-47012 | 7.8 HIGH | RDMA/siw: Fix a use after free in siw_alloc_mr |
| CVE-2021-47011 | 7.8 HIGH | mm: memcontrol: slab: fix obtain a reference to a freeing memcg |
| CVE-2020-36787 | 7.8 HIGH | media: aspeed: fix clock handling logic |
| CVE-2021-47041 | 7.5 HIGH | nvmet-tcp: fix incorrect locking in state_change sk callback |
| CVE-2021-46983 | 7.5 HIGH | nvmet-rdma: Fix NULL deref when SEND is completed with error |
Showing top 20 of 86 CVEs. View all on vendor page → →
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Same vendor: Linux
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CVE-2026-98384
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V. Comments for CVE-2021-46989
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