The patch titled
Subject: fs/proc/task_mmu: move mmu notification mechanism inside mm lock
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Subject: fs/proc/task_mmu: move mmu notification mechanism inside mm lock
Date: Tue, 9 Jan 2024 16:24:42 +0500
Move mmu notification mechanism inside mm lock to prevent race condition
in other components which depend on it. The notifier will invalidate
memory range. Depending upon the number of iterations, different memory
ranges would be invalidated.
The following warning would be removed by this patch:
WARNING: CPU: 0 PID: 5067 at arch/x86/kvm/../../../virt/kvm/kvm_main.c:734 kvm_mmu_notifier_change_pte+0x860/0x960 arch/x86/kvm/../../../virt/kvm/kvm_main.c:734
There is no behavioural and performance change with this patch when
there is no component registered with the mmu notifier.
Link: https://lkml.kernel.org/r/20240109112445.590736-1-usama.anjum@xxxxxxxxxxxxx
Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Reported-by: syzbot+81227d2bd69e9dedb802@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/000000000000f6d051060c6785bc@xxxxxxxxxx/
Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: MichaÅ? MirosÅ?aw <mirq-linux@xxxxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
--- a/fs/proc/task_mmu.c~fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock
+++ a/fs/proc/task_mmu.c
@@ -2448,13 +2448,6 @@ static long do_pagemap_scan(struct mm_st
if (ret)
return ret;
- /* Protection change for the range is going to happen. */
- if (p.arg.flags & PM_SCAN_WP_MATCHING) {
- mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
- mm, p.arg.start, p.arg.end);
- mmu_notifier_invalidate_range_start(&range);
- }
-
for (walk_start = p.arg.start; walk_start < p.arg.end;
walk_start = p.arg.walk_end) {
long n_out;
@@ -2467,8 +2460,20 @@ static long do_pagemap_scan(struct mm_st
ret = mmap_read_lock_killable(mm);
if (ret)
break;
+
+ /* Protection change for the range is going to happen. */
+ if (p.arg.flags & PM_SCAN_WP_MATCHING) {
+ mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
+ mm, walk_start, p.arg.end);
+ mmu_notifier_invalidate_range_start(&range);
+ }
+
ret = walk_page_range(mm, walk_start, p.arg.end,
&pagemap_scan_ops, &p);
+
+ if (p.arg.flags & PM_SCAN_WP_MATCHING)
+ mmu_notifier_invalidate_range_end(&range);
+
mmap_read_unlock(mm);
n_out = pagemap_scan_flush_buffer(&p);
@@ -2494,9 +2499,6 @@ static long do_pagemap_scan(struct mm_st
if (pagemap_scan_writeback_args(&p.arg, uarg))
ret = -EFAULT;
- if (p.arg.flags & PM_SCAN_WP_MATCHING)
- mmu_notifier_invalidate_range_end(&range);
-
kfree(p.vec_buf);
return ret;
}
_
Patches currently in -mm which might be from usama.anjum@xxxxxxxxxxxxx are
fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock.patch
