CVE-2023-52476 perf/x86/lbr: Filter vsyscall addresses
A local attacker can cause a kernel panic by triggering a null dereference in the Linux kernel's LBR sampling when a vsyscall is interrupted.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-52476?
CVE-2023-52476 is a medium-severity vulnerability in Linux kernel, published on 29 Feb 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2023-52476?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2023-52476?
Apply the vendor's patch.
Is CVE-2023-52476 being exploited?
There is no known exploitation of CVE-2023-52476 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2023-52476, DEBIAN-CVE-2023-52476, GHSA-p6q6-7q65-mgx6, ROOT-OS-DEBIAN-11-CVE-2023-52476, UBUNTU-CVE-2023-52476.