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Howlett" , Vlastimil Babka , Lorenzo Stoakes , Shuah Khan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, jeffxu@chromium.org, oliver.sang@intel.com, torvalds@linux-foundation.org, Michael Ellerman , Kees Cook , Pedro Falcato X-Mailer: b4 0.14.1 Replace can_modify_mm_madv() with a single vma variant, and associated checks in madvise. While we're at it, also invert the order of checks in: if (unlikely(is_ro_anon(vma) && !can_modify_vma(vma)) Checking if we can modify the vma itself (through vm_flags) is certainly cheaper than is_ro_anon() due to arch_vma_access_permitted() looking at e.g pkeys registers (with extra branches) in some architectures. This patch allows for partial madvise success when finding a sealed VMA, which historically has been allowed in Linux. Signed-off-by: Pedro Falcato Reviewed-by: Liam R. Howlett --- mm/internal.h | 2 -- mm/madvise.c | 13 +++---------- mm/mseal.c | 17 ++++------------- mm/vma.h | 7 +++++++ 4 files changed, 14 insertions(+), 25 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index ca422aede342..1db320650539 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1363,8 +1363,6 @@ static inline int can_do_mseal(unsigned long flags) bool can_modify_mm(struct mm_struct *mm, unsigned long start, unsigned long end); -bool can_modify_mm_madv(struct mm_struct *mm, unsigned long start, - unsigned long end, int behavior); #else static inline int can_do_mseal(unsigned long flags) { diff --git a/mm/madvise.c b/mm/madvise.c index 89089d84f8df..4e64770be16c 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1031,6 +1031,9 @@ static int madvise_vma_behavior(struct vm_area_struct *vma, struct anon_vma_name *anon_name; unsigned long new_flags = vma->vm_flags; + if (unlikely(!can_modify_vma_madv(vma, behavior))) + return -EPERM; + switch (behavior) { case MADV_REMOVE: return madvise_remove(vma, prev, start, end); @@ -1448,15 +1451,6 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh start = untagged_addr_remote(mm, start); end = start + len; - /* - * Check if the address range is sealed for do_madvise(). - * can_modify_mm_madv assumes we have acquired the lock on MM. - */ - if (unlikely(!can_modify_mm_madv(mm, start, end, behavior))) { - error = -EPERM; - goto out; - } - blk_start_plug(&plug); switch (behavior) { case MADV_POPULATE_READ: @@ -1470,7 +1464,6 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh } blk_finish_plug(&plug); -out: if (write) mmap_write_unlock(mm); else diff --git a/mm/mseal.c b/mm/mseal.c index 2170e2139ca0..fdd1666344fa 100644 --- a/mm/mseal.c +++ b/mm/mseal.c @@ -75,24 +75,15 @@ bool can_modify_mm(struct mm_struct *mm, unsigned long start, unsigned long end) } /* - * Check if the vmas of a memory range are allowed to be modified by madvise. - * the memory ranger can have a gap (unallocated memory). - * return true, if it is allowed. + * Check if a vma is allowed to be modified by madvise. */ -bool can_modify_mm_madv(struct mm_struct *mm, unsigned long start, unsigned long end, - int behavior) +bool can_modify_vma_madv(struct vm_area_struct *vma, int behavior) { - struct vm_area_struct *vma; - - VMA_ITERATOR(vmi, mm, start); - if (!is_madv_discard(behavior)) return true; - /* going through each vma to check. */ - for_each_vma_range(vmi, vma, end) - if (unlikely(is_ro_anon(vma) && !can_modify_vma(vma))) - return false; + if (unlikely(!can_modify_vma(vma) && is_ro_anon(vma))) + return false; /* Allow by default. */ return true; diff --git a/mm/vma.h b/mm/vma.h index e979015cc7fc..da31d0f62157 100644 --- a/mm/vma.h +++ b/mm/vma.h @@ -380,6 +380,8 @@ static inline bool can_modify_vma(struct vm_area_struct *vma) return true; } +bool can_modify_vma_madv(struct vm_area_struct *vma, int behavior); + #else static inline bool can_modify_vma(struct vm_area_struct *vma) @@ -387,6 +389,11 @@ static inline bool can_modify_vma(struct vm_area_struct *vma) return true; } +static inline bool can_modify_vma_madv(struct vm_area_struct *vma, int behavior) +{ + return true; +} + #endif #endif /* __MM_VMA_H */