mseal: replace can_modify_mm_madv with a vma variant
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.
Link: https://lkml.kernel.org/r/20240817-mseal-depessimize-v3-5-d8d2e037df30@gmail.com
Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/mm/internal.h b/mm/internal.h
index cbe4849..241cf46 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1361,8 +1361,6 @@ 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 89089d8..4e64770 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 2170e213..fdd1666 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 e979015..da31d0f 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 */
