The patch titled
Subject: mseal: replace can_modify_mm_madv with a vma variant
has been added to the -mm mm-unstable branch. Its filename is
mseal-replace-can_modify_mm_madv-with-a-vma-variant.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mseal-replace-can_modify_mm_madv-with-a-vma-variant.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Pedro Falcato <pedro.falcato@xxxxxxxxx>
Subject: mseal: replace can_modify_mm_madv with a vma variant
Date: Sat, 17 Aug 2024 01:18:32 +0100
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@xxxxxxxxx
Signed-off-by: Pedro Falcato <pedro.falcato@xxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Jeff Xu <jeffxu@xxxxxxxxxxxx>
Cc: Kees Cook <kees@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/internal.h | 2 --
mm/madvise.c | 13 +++----------
mm/mseal.c | 17 ++++-------------
mm/vma.h | 7 +++++++
4 files changed, 14 insertions(+), 25 deletions(-)
--- a/mm/internal.h~mseal-replace-can_modify_mm_madv-with-a-vma-variant
+++ a/mm/internal.h
@@ -1370,8 +1370,6 @@ static inline int can_do_mseal(unsigned
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)
{
--- a/mm/madvise.c~mseal-replace-can_modify_mm_madv-with-a-vma-variant
+++ a/mm/madvise.c
@@ -1031,6 +1031,9 @@ static int madvise_vma_behavior(struct v
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, uns
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, uns
}
blk_finish_plug(&plug);
-out:
if (write)
mmap_write_unlock(mm);
else
--- a/mm/mseal.c~mseal-replace-can_modify_mm_madv-with-a-vma-variant
+++ a/mm/mseal.c
@@ -75,24 +75,15 @@ bool can_modify_mm(struct mm_struct *mm,
}
/*
- * 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;
--- a/mm/vma.h~mseal-replace-can_modify_mm_madv-with-a-vma-variant
+++ a/mm/vma.h
@@ -380,12 +380,19 @@ static inline bool can_modify_vma(struct
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)
{
return true;
}
+
+static inline bool can_modify_vma_madv(struct vm_area_struct *vma, int behavior)
+{
+ return true;
+}
#endif
_
Patches currently in -mm which might be from pedro.falcato@xxxxxxxxx are
selftests-mm-add-mseal-test-for-no-discard-madvise.patch
selftests-mm-add-mseal-test-for-no-discard-madvise-fix.patch
mm-move-can_modify_vma-to-mm-vmah.patch
mm-munmap-replace-can_modify_mm-with-can_modify_vma.patch
mm-mprotect-replace-can_modify_mm-with-can_modify_vma.patch
mm-mremap-replace-can_modify_mm-with-can_modify_vma.patch
mseal-replace-can_modify_mm_madv-with-a-vma-variant.patch
mm-remove-can_modify_mm.patch
selftests-mm-add-more-mseal-traversal-tests.patch
