From: Pingfan Liu kernelfans@gmail.com
commit d3eb70ead6474ec16f976fcacf10a7a890a95bd3 upstream.
trans_pgd_create_copy() can hit "VM_BUG_ON(mm != &init_mm)" in the function pmd_populate_kernel().
This is the combined consequence of commit 5de59884ac0e ("arm64: trans_pgd: pass NULL instead of init_mm to *_populate functions"), which replaced &init_mm with NULL and commit 59511cfd08f3 ("arm64: mm: use XN table mapping attributes for user/kernel mappings"), which introduced the VM_BUG_ON.
Since the former sounds reasonable, it is better to work on the later.
From the perspective of trans_pgd, two groups of functions are
considered in the later one:
pmd_populate_kernel() mm == NULL should be fixed, else it hits VM_BUG_ON() p?d_populate() mm == NULL means PXN, that is OK, since trans_pgd only copies a linear map, no execution will happen on the map.
So it is good enough to just relax VM_BUG_ON() to disregard mm == NULL
Fixes: 59511cfd08f3 ("arm64: mm: use XN table mapping attributes for user/kernel mappings") Signed-off-by: Pingfan Liu kernelfans@gmail.com Cc: stable@vger.kernel.org # 5.13.x Cc: Ard Biesheuvel ardb@kernel.org Cc: James Morse james.morse@arm.com Cc: Matthias Brugger mbrugger@suse.com Reviewed-by: Catalin Marinas catalin.marinas@arm.com Reviewed-by: Pasha Tatashin pasha.tatashin@soleen.com Link: https://lore.kernel.org/r/20211112052214.9086-1-kernelfans@gmail.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/pgalloc.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arm64/include/asm/pgalloc.h +++ b/arch/arm64/include/asm/pgalloc.h @@ -76,7 +76,7 @@ static inline void __pmd_populate(pmd_t static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep) { - VM_BUG_ON(mm != &init_mm); + VM_BUG_ON(mm && mm != &init_mm); __pmd_populate(pmdp, __pa(ptep), PMD_TYPE_TABLE | PMD_TABLE_UXN); }