CVE-2024-26850

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

mm/debugvmpgtable: fix BUG_ON with pud advanced test

Architectures like powerpc add debug checks to ensure we find only devmap PUD pte entries. These debug checks are only done with CONFIGDEBUGVM. This patch marks the ptes used for PUD advanced test devmap pte entries so that we don't hit on debug checks on architecture like ppc64 as below.

WARNING: CPU: 2 PID: 1 at arch/powerpc/mm/book3s64/radixpgtable.c:1382 radixpudhugepageupdate+0x38/0x138 .... NIP [c0000000000a7004] radixpudhugepageupdate+0x38/0x138 LR [c0000000000a77a8] radixpudphugegetandclear+0x28/0x60 Call Trace: [c000000004a2f950] [c000000004a2f9a0] 0xc000000004a2f9a0 (unreliable) [c000000004a2f980] [000d34c100000000] 0xd34c100000000 [c000000004a2f9a0] [c00000000206ba98] pudadvancedtests+0x118/0x334 [c000000004a2fa40] [c00000000206db34] debugvmpgtable+0xcbc/0x1c48 [c000000004a2fc10] [c00000000000fd28] doone_initcall+0x60/0x388

Also

kernel BUG at arch/powerpc/mm/book3s64/pgtable.c:202! ....

NIP [c000000000096510] pudphugegetandclearfull+0x98/0x174 LR [c00000000206bb34] pudadvancedtests+0x1b4/0x334 Call Trace: [c000000004a2f950] [000d34c100000000] 0xd34c100000000 (unreliable) [c000000004a2f9a0] [c00000000206bb34] pudadvancedtests+0x1b4/0x334 [c000000004a2fa40] [c00000000206db34] debugvmpgtable+0xcbc/0x1c48 [c000000004a2fc10] [c00000000000fd28] doone_initcall+0x60/0x388