github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-23 06:31:58 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

arm64/mm: Sanity check PTE address before runtime P4D/PUD folding

Browse Source 
The runtime P4D/PUD folding logic assumes that the respective pgd_t* and
p4d_t* arguments are pointers into actual page tables that are part of
the hierarchy being operated on.

This may not always be the case, and we have been bitten once by this
already [0], where the argument was actually a stack variable, and in
this case, the logic does not work at all.

So let's add a VM_BUG_ON() for each case, to ensure that the address of
the provided page table entry is consistent with the address being
translated.

[0] https://lore.kernel.org/all/20240725090345.28461-1-will@kernel.org/T/#u

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20241105093919.1312049-2-ardb+git@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ard Biesheuvel 2024-11-05 10:39:20 +01:00 committed by Catalin Marinas
parent ced841702e
commit baec239797
1 changed files with 6 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/arm64/include/asm/pgtable.h
View File

@ -921,6 +921,9 @@ static inline phys_addr_t p4d_page_paddr(p4d_t p4d)
static inline pud_t *p4d_to_folded_pud(p4d_t *p4dp, unsigned long addr)
{
/* Ensure that 'p4dp' indexes a page table according to 'addr' */
VM_BUG_ON(((addr >> P4D_SHIFT) ^ ((u64)p4dp >> 3)) % PTRS_PER_P4D);
return (pud_t *)PTR_ALIGN_DOWN(p4dp, PAGE_SIZE) + pud_index(addr);
}
@ -1045,6 +1048,9 @@ static inline phys_addr_t pgd_page_paddr(pgd_t pgd)
static inline p4d_t *pgd_to_folded_p4d(pgd_t *pgdp, unsigned long addr)
{
/* Ensure that 'pgdp' indexes a page table according to 'addr' */
VM_BUG_ON(((addr >> PGDIR_SHIFT) ^ ((u64)pgdp >> 3)) % PTRS_PER_PGD);
return (p4d_t *)PTR_ALIGN_DOWN(pgdp, PAGE_SIZE) + p4d_index(addr);
}