From 5baf8b037debf4ec60108ccfeccb8636d1dbad81 Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Tue, 29 Oct 2024 18:11:47 +0000 Subject: mm: refactor arch_calc_vm_flag_bits() and arm64 MTE handling Currently MTE is permitted in two circumstances (desiring to use MTE having been specified by the VM_MTE flag) - where MAP_ANONYMOUS is specified, as checked by arch_calc_vm_flag_bits() and actualised by setting the VM_MTE_ALLOWED flag, or if the file backing the mapping is shmem, in which case we set VM_MTE_ALLOWED in shmem_mmap() when the mmap hook is activated in mmap_region(). The function that checks that, if VM_MTE is set, VM_MTE_ALLOWED is also set is the arm64 implementation of arch_validate_flags(). Unfortunately, we intend to refactor mmap_region() to perform this check earlier, meaning that in the case of a shmem backing we will not have invoked shmem_mmap() yet, causing the mapping to fail spuriously. It is inappropriate to set this architecture-specific flag in general mm code anyway, so a sensible resolution of this issue is to instead move the check somewhere else. We resolve this by setting VM_MTE_ALLOWED much earlier in do_mmap(), via the arch_calc_vm_flag_bits() call. This is an appropriate place to do this as we already check for the MAP_ANONYMOUS case here, and the shmem file case is simply a variant of the same idea - we permit RAM-backed memory. This requires a modification to the arch_calc_vm_flag_bits() signature to pass in a pointer to the struct file associated with the mapping, however this is not too egregious as this is only used by two architectures anyway - arm64 and parisc. So this patch performs this adjustment and removes the unnecessary assignment of VM_MTE_ALLOWED in shmem_mmap(). [akpm@linux-foundation.org: fix whitespace, per Catalin] Link: https://lkml.kernel.org/r/ec251b20ba1964fb64cf1607d2ad80c47f3873df.1730224667.git.lorenzo.stoakes@oracle.com Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails") Signed-off-by: Lorenzo Stoakes Suggested-by: Catalin Marinas Reported-by: Jann Horn Reviewed-by: Catalin Marinas Reviewed-by: Vlastimil Babka Cc: Andreas Larsson Cc: David S. Miller Cc: Helge Deller Cc: James E.J. Bottomley Cc: Liam R. Howlett Cc: Linus Torvalds Cc: Mark Brown Cc: Peter Xu Cc: Will Deacon Cc: Signed-off-by: Andrew Morton --- include/linux/mman.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/mman.h b/include/linux/mman.h index 8ddca62d6460..a842783ffa62 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -2,6 +2,7 @@ #ifndef _LINUX_MMAN_H #define _LINUX_MMAN_H +#include #include #include @@ -94,7 +95,7 @@ static inline void vm_unacct_memory(long pages) #endif #ifndef arch_calc_vm_flag_bits -#define arch_calc_vm_flag_bits(flags) 0 +#define arch_calc_vm_flag_bits(file, flags) 0 #endif #ifndef arch_validate_prot @@ -151,13 +152,13 @@ calc_vm_prot_bits(unsigned long prot, unsigned long pkey) * Combine the mmap "flags" argument into "vm_flags" used internally. */ static inline unsigned long -calc_vm_flag_bits(unsigned long flags) +calc_vm_flag_bits(struct file *file, unsigned long flags) { return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) | _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) | _calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) | _calc_vm_trans(flags, MAP_STACK, VM_NOHUGEPAGE) | - arch_calc_vm_flag_bits(flags); + arch_calc_vm_flag_bits(file, flags); } unsigned long vm_commit_limit(void); -- cgit v1.2.3