arm64: compat: Do not treat syscall number as ESR_ELx for a bad syscall

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2022-49520
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-02-26 07:01:28 UTC
Updated2026-08-15 13:17:23 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: arm64: compat: Do not treat syscall number as ESR_ELx for a bad syscall If a compat process tries to execute an unknown system call above the __ARM_NR_COMPAT_END number, the kernel sends a SIGILL signal to the offending process. Information about the error is printed to dmesg in compat_arm_syscall() -> arm64_notify_die() -> arm64_force_sig_fault() -> arm64_show_signal(). arm64_show_signal() interprets a non-zero value for current->thread.fault_code as an exception syndrome and displays the message associated with the ESR_ELx.EC field (bits 31:26). current->thread.fault_code is set in compat_arm_syscall() -> arm64_notify_die() with the bad syscall number instead of a valid ESR_ELx value. This means that the ESR_ELx.EC field has the value that the user set for the syscall number and the kernel can end up printing bogus exception messages*. For example, for the syscall number 0x68000000, which evaluates to ESR_ELx.EC value of 0x1A (ESR_ELx_EC_FPAC) the kernel prints this error: [ 18.349161] syscall[300]: unhandled exception: ERET/ERETAA/ERETAB, ESR 0x68000000, Oops - bad compat syscall(2) in syscall[10000+50000] [ 18.350639] CPU: 2 PID: 300 Comm: syscall Not tainted 5.18.0-rc1 #79 [ 18.351249] Hardware name: Pine64 RockPro64 v2.0 (DT) [..] which is misleading, as the bad compat syscall has nothing to do with pointer authentication. Stop arm64_show_signal() from printing exception syndrome information by having compat_arm_syscall() set the ESR_ELx value to 0, as it has no meaning for an invalid system call number. The example above now becomes: [ 19.935275] syscall[301]: unhandled exception: Oops - bad compat syscall(2) in syscall[10000+50000] [ 19.936124] CPU: 1 PID: 301 Comm: syscall Not tainted 5.18.0-rc1-00005-g7e08006d4102 #80 [ 19.936894] Hardware name: Pine64 RockPro64 v2.0 (DT) [..] which although shows less information because the syscall number, wrongfully advertised as the ESR value, is missing, it is better than showing plainly wrong information. The syscall number can be easily obtained with strace. *A 32-bit value above or equal to 0x8000_0000 is interpreted as a negative integer in compat_arm_syscal() and the condition scno < __ARM_NR_COMPAT_END evaluates to true; the syscall will exit to userspace in this case with the ENOSYS error code instead of arm64_notify_die() being called.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 532826f3712b607256eb30f92f23d1c604d3fa34 efd183d988b416fcdf6f7c298a17ced4859ca77d git Not specified
CNA Linux Linux affected 532826f3712b607256eb30f92f23d1c604d3fa34 ad97425d23af3c3b8d4f6a2bb666cb485087c007 git Not specified
CNA Linux Linux affected 532826f3712b607256eb30f92f23d1c604d3fa34 621916afe8cd4f322eb12759b64a2f938d4e551d git Not specified
CNA Linux Linux affected 532826f3712b607256eb30f92f23d1c604d3fa34 095e975f8150ccd7f852eb578c1cdbdd2f517c7a git Not specified
CNA Linux Linux affected 532826f3712b607256eb30f92f23d1c604d3fa34 3910ae71cb963fa2b68e684489d4fc3d105afda0 git Not specified
CNA Linux Linux affected 532826f3712b607256eb30f92f23d1c604d3fa34 3fed9e551417b84038b15117732ea4505eee386b git Not specified
CNA Linux Linux affected 4.17 Not specified
CNA Linux Linux unaffected 4.17 semver Not specified
CNA Linux Linux unaffected 5.4.198 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.121 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.46 5.15.* semver Not specified
CNA Linux Linux unaffected 5.17.14 5.17.* semver Not specified
CNA Linux Linux unaffected 5.18.3 5.18.* semver Not specified
CNA Linux Linux unaffected 5.19 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/efd183d988b416fcdf6f7c298a17ced4859ca77d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/3910ae71cb963fa2b68e684489d4fc3d105afda0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/621916afe8cd4f322eb12759b64a2f938d4e551d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/ad97425d23af3c3b8d4f6a2bb666cb485087c007 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/095e975f8150ccd7f852eb578c1cdbdd2f517c7a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/3fed9e551417b84038b15117732ea4505eee386b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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