CVE-2022-49264 (GCVE-0-2022-49264)
Vulnerability from cvelistv5
Published
2025-02-26 01:56
Modified
2025-05-04 08:33
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
exec: Force single empty string when argv is empty
Quoting[1] Ariadne Conill:
"In several other operating systems, it is a hard requirement that the
second argument to execve(2) be the name of a program, thus prohibiting
a scenario where argc < 1. POSIX 2017 also recommends this behaviour,
but it is not an explicit requirement[2]:
The argument arg0 should point to a filename string that is
associated with the process being started by one of the exec
functions.
...
Interestingly, Michael Kerrisk opened an issue about this in 2008[3],
but there was no consensus to support fixing this issue then.
Hopefully now that CVE-2021-4034 shows practical exploitative use[4]
of this bug in a shellcode, we can reconsider.
This issue is being tracked in the KSPP issue tracker[5]."
While the initial code searches[6][7] turned up what appeared to be
mostly corner case tests, trying to that just reject argv == NULL
(or an immediately terminated pointer list) quickly started tripping[8]
existing userspace programs.
The next best approach is forcing a single empty string into argv and
adjusting argc to match. The number of programs depending on argc == 0
seems a smaller set than those calling execve with a NULL argv.
Account for the additional stack space in bprm_stack_limits(). Inject an
empty string when argc == 0 (and set argc = 1). Warn about the case so
userspace has some notice about the change:
process './argc0' launched './argc0' with NULL argv: empty string added
Additionally WARN() and reject NULL argv usage for kernel threads.
[1] https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@dereferenced.org/
[2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
[3] https://bugzilla.kernel.org/show_bug.cgi?id=8408
[4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt
[5] https://github.com/KSPP/linux/issues/176
[6] https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL&literal=0
[7] https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%2C%5Cs*NULL&literal=0
[8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ▼ | Linux | Linux |
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 |
||||||
|
|||||||||
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nexec: Force single empty string when argv is empty\n\nQuoting[1] Ariadne Conill:\n\n\"In several other operating systems, it is a hard requirement that the\nsecond argument to execve(2) be the name of a program, thus prohibiting\na scenario where argc \u003c 1. POSIX 2017 also recommends this behaviour,\nbut it is not an explicit requirement[2]:\n\n The argument arg0 should point to a filename string that is\n associated with the process being started by one of the exec\n functions.\n...\nInterestingly, Michael Kerrisk opened an issue about this in 2008[3],\nbut there was no consensus to support fixing this issue then.\nHopefully now that CVE-2021-4034 shows practical exploitative use[4]\nof this bug in a shellcode, we can reconsider.\n\nThis issue is being tracked in the KSPP issue tracker[5].\"\n\nWhile the initial code searches[6][7] turned up what appeared to be\nmostly corner case tests, trying to that just reject argv == NULL\n(or an immediately terminated pointer list) quickly started tripping[8]\nexisting userspace programs.\n\nThe next best approach is forcing a single empty string into argv and\nadjusting argc to match. The number of programs depending on argc == 0\nseems a smaller set than those calling execve with a NULL argv.\n\nAccount for the additional stack space in bprm_stack_limits(). Inject an\nempty string when argc == 0 (and set argc = 1). Warn about the case so\nuserspace has some notice about the change:\n\n process \u0027./argc0\u0027 launched \u0027./argc0\u0027 with NULL argv: empty string added\n\nAdditionally WARN() and reject NULL argv usage for kernel threads.\n\n[1] https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@dereferenced.org/\n[2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html\n[3] https://bugzilla.kernel.org/show_bug.cgi?id=8408\n[4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt\n[5] https://github.com/KSPP/linux/issues/176\n[6] https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL\u0026literal=0\n[7] https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%2C%5Cs*NULL\u0026literal=0\n[8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/"
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