CVE-2024-50254

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Source
https://nvd.nist.gov/vuln/detail/CVE-2024-50254
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2024-50254.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2024-50254
Downstream
Related
Published
2024-11-09T10:15:07Z
Modified
2025-10-17T16:08:59.186980Z
Severity
  • 5.5 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
bpf: Free dynamically allocated bits in bpf_iter_bits_destroy()
Details

In the Linux kernel, the following vulnerability has been resolved:

bpf: Free dynamically allocated bits in bpfiterbits_destroy()

bpfiterbitsdestroy() uses "kit->nrbits <= 64" to check whether the bits are dynamically allocated. However, the check is incorrect and may cause a kmemleak as shown below:

unreferenced object 0xffff88812628c8c0 (size 32): comm "swapper/0", pid 1, jiffies 4294727320 hex dump (first 32 bytes): b0 c1 55 f5 81 88 ff ff f0 f0 f0 f0 f0 f0 f0 f0 ..U........... f0 f0 f0 f0 f0 f0 f0 f0 00 00 00 00 00 00 00 00 .............. backtrace (crc 781e32cc): [<00000000c452b4ab>] kmemleakalloc+0x4b/0x80 [<0000000004e09f80>] _kmallocnodenoprof+0x480/0x5c0 [<00000000597124d6>] _alloc.isra.0+0x89/0xb0 [<000000004ebfffcd>] allocbulk+0x2af/0x720 [<00000000d9c10145>] prefillmemcache+0x7f/0xb0 [<00000000ff9738ff>] bpfmemallocinit+0x3e2/0x610 [<000000008b616eac>] bpfglobalmainit+0x19/0x30 [<00000000fc473efc>] dooneinitcall+0xd3/0x3c0 [<00000000ec81498c>] kernelinitfreeable+0x66a/0x940 [<00000000b119f72f>] kernelinit+0x20/0x160 [<00000000f11ac9a7>] retfromfork+0x3c/0x70 [<0000000004671da4>] retfromforkasm+0x1a/0x30

That is because nrbits will be set as zero in bpfiterbitsnext() after all bits have been iterated.

Fix the issue by setting kit->bit to kit->nrbits instead of setting kit->nrbits to zero when the iteration completes in bpfiterbitsnext(). In addition, use "!nrbits || bits >= nrbits" to check whether the iteration is complete and still use "nrbits > 64" to indicate whether bits are dynamically allocated. The "!nrbits" check is necessary because bpfiterbitsnew() may fail before setting kit->nr_bits, and this condition will stop the iteration early instead of accessing the zeroed or freed kit->bits.

Considering the initial value of kit->bits is -1 and the type of kit->nrbits is unsigned int, change the type of kit->nrbits to int. The potential overflow problem will be handled in the following patch.

References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4665415975b0827e9646cab91c61d02a6b364d59
Fixed
9cee266fafaf79fd465314546f637f9a3c215830
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4665415975b0827e9646cab91c61d02a6b364d59
Fixed
101ccfbabf4738041273ce64e2b116cf440dea13

Affected versions

v6.*

v6.10
v6.10-rc1
v6.10-rc2
v6.10-rc3
v6.10-rc4
v6.10-rc5
v6.10-rc6
v6.10-rc7
v6.11
v6.11-rc1
v6.11-rc2
v6.11-rc3
v6.11-rc4
v6.11-rc5
v6.11-rc6
v6.11-rc7
v6.11.1
v6.11.2
v6.11.3
v6.11.4
v6.11.5
v6.11.6
v6.12-rc1
v6.12-rc2
v6.12-rc3
v6.12-rc4

Database specific

vanir_signatures

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        "deprecated": false,
        "signature_version": "v1",
        "signature_type": "Function",
        "id": "CVE-2024-50254-25c05375",
        "target": {
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            "function": "bpf_iter_bits_next"
        }
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]

Linux / Kernel

Package

Name
Kernel

Affected ranges

Type
ECOSYSTEM
Events
Introduced
6.11.0
Fixed
6.11.7