From 4cccb6221cae6d020270606b9e52b1678fc8b71a Mon Sep 17 00:00:00 2001 From: Muhammad Usama Anjum Date: Tue, 9 Jan 2024 16:24:42 +0500 Subject: fs/proc/task_mmu: move mmu notification mechanism inside mm lock MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. [akpm@linux-foundation.org: narrow the scope of `range', per Sean] Link: https://lkml.kernel.org/r/20240109112445.590736-1-usama.anjum@collabora.com Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs") Signed-off-by: Muhammad Usama Anjum Reported-by: syzbot+81227d2bd69e9dedb802@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/000000000000f6d051060c6785bc@google.com/ Reviewed-by: Sean Christopherson Cc: Andrei Vagin Cc: Arnd Bergmann Cc: David Hildenbrand Cc: Hugh Dickins Cc: Kefeng Wang Cc: Liam R. Howlett Cc: Michał Mirosław Cc: Peter Xu Cc: Ryan Roberts Cc: Stephen Rothwell Cc: Suren Baghdasaryan Cc: Signed-off-by: Andrew Morton --- fs/proc/task_mmu.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) (limited to 'fs/proc') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 62b16f42d5d2..3f78ebbb795f 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -2432,7 +2432,6 @@ static long pagemap_scan_flush_buffer(struct pagemap_scan_private *p) static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) { - struct mmu_notifier_range range; struct pagemap_scan_private p = {0}; unsigned long walk_start; size_t n_ranges_out = 0; @@ -2448,15 +2447,9 @@ static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) 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) { + struct mmu_notifier_range range; long n_out; if (fatal_signal_pending(current)) { @@ -2467,8 +2460,20 @@ static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) 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_struct *mm, unsigned long uarg) 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; } -- cgit v1.2.3