Description

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

perf/x86/lbr: Filter vsyscall addresses

We found that a panic can occur when a vsyscall is made while LBR sampling
is active. If the vsyscall is interrupted (NMI) for perf sampling, this
call sequence can occur (most recent at top):

__insn_get_emulate_prefix()
insn_get_emulate_prefix()
insn_get_prefixes()
insn_get_opcode()
decode_branch_type()
get_branch_type()
intel_pmu_lbr_filter()
intel_pmu_handle_irq()
perf_event_nmi_handler()

Within __insn_get_emulate_prefix() at frame 0, a macro is called:

peek_nbyte_next(insn_byte_t, insn, i)

Within this macro, this dereference occurs:

(insn)->next_byte

Inspecting registers at this point, the value of the next_byte field is the
address of the vsyscall made, for example the location of the vsyscall
version of gettimeofday() at 0xffffffffff600000. The access to an address
in the vsyscall region will trigger an oops due to an unhandled page fault.

To fix the bug, filtering for vsyscalls can be done when
determining the branch type. This patch will return
a "none" branch if a kernel address if found to lie in the
vsyscall region.

Classification

CVE ID: CVE-2023-52476

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.06% (scored less or equal to compared to others)

EPSS Date: 2025-02-03 (when was this score calculated)

References

https://git.kernel.org/stable/c/403d201d1fd144cb249836dafb222f6375871c6c
https://git.kernel.org/stable/c/3863989497652488a50f00e96de4331e5efabc6c
https://git.kernel.org/stable/c/f71edacbd4f99c0e12fe4a4007ab4d687d0688db
https://git.kernel.org/stable/c/e53899771a02f798d436655efbd9d4b46c0f9265

Timeline