CVE-2024-56678: powerpc/mm/fault: Fix kfence page fault reporting
In the Linux kernel, the following vulnerability has been resolved:
powerpc/mm/fault: Fix kfence page fault reporting
copyfromkernelnofault() can be called when doing read of /proc/kcore. /proc/kcore can have some unmapped kfence objects which when read via copyfromkernelnofault() can cause page faults. Since nofault() functions define their own fixup table for handling fault, use that instead of asking kfence to handle such faults.
Hence we search the exception tables for the nip which generated the fault. If there is an entry then we let the fixup table handler handle the page fault by returning an error from within dopagefault().
This can be easily triggered if someone tries to do dd from /proc/kcore. eg. dd if=/proc/kcore of=/dev/null bs=1M
Some example false negatives:
=============================== BUG: KFENCE: invalid read in copyfromkernelnofault+0x9c/0x1a0 Invalid read at 0xc0000000fdff0000: copyfromkernelnofault+0x9c/0x1a0 0xc00000000665f950 readkcoreiter+0x57c/0xa04 procregreaditer+0xe4/0x16c vfsread+0x320/0x3ec ksysread+0x90/0x154 systemcallexception+0x120/0x310 systemcallvectoredcommon+0x15c/0x2ec
BUG: KFENCE: use-after-free read in copyfromkernelnofault+0x9c/0x1a0 Use-after-free read at 0xc0000000fe050000 (in kfence-#2): copyfromkernelnofault+0x9c/0x1a0 0xc00000000665f950 readkcoreiter+0x57c/0xa04 procregreaditer+0xe4/0x16c vfsread+0x320/0x3ec ksysread+0x90/0x154 systemcallexception+0x120/0x310 systemcallvectoredcommon+0x15c/0x2ec
Other sources
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— Launchpad
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2024-56678?
CVE-2024-56678 is classified as a high severity vulnerability within the Linux kernel.
How do I fix CVE-2024-56678?
To resolve CVE-2024-56678, update your Linux kernel to the latest stable version recommended by your distribution.
What systems are affected by CVE-2024-56678?
CVE-2024-56678 affects all versions of the Linux kernel that include the faulty handling of kfence page fault reporting.
What is the potential impact of exploiting CVE-2024-56678?
Exploiting CVE-2024-56678 could lead to unauthorized access to memory contents, potentially exposing sensitive information.
When was CVE-2024-56678 discovered?
CVE-2024-56678 was reported and addressed in recent patches in 2024.