The patch titled Subject: hugetlb: check for anon_vma prior to folio allocation has been added to the -mm mm-hotfixes-unstable branch. Its filename is hugetlb-check-for-anon_vma-prior-to-folio-allocation.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

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: "Vishal Moola (Oracle)" vishal.moola@gmail.com Subject: hugetlb: check for anon_vma prior to folio allocation Date: Mon, 15 Apr 2024 14:17:47 -0700

Commit 9acad7ba3e25 ("hugetlb: use vmf_anon_prepare() instead of anon_vma_prepare()") may bailout after allocating a folio if we do not hold the mmap lock. When this occurs, vmf_anon_prepare() will release the vma lock. Hugetlb then attempts to call restore_reserve_on_error(), which depends on the vma lock being held.

We can move vmf_anon_prepare() prior to the folio allocation in order to avoid calling restore_reserve_on_error() without the vma lock.

Link: https://lkml.kernel.org/r/ZiFqSrSRLhIV91og@fedora Fixes: 9acad7ba3e25 ("hugetlb: use vmf_anon_prepare() instead of anon_vma_prepare()") Reported-by: syzbot+ad1b592fc4483655438b@syzkaller.appspotmail.com Signed-off-by: Vishal Moola (Oracle) vishal.moola@gmail.com Cc: Muchun Song muchun.song@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/hugetlb.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/mm/hugetlb.c~hugetlb-check-for-anon_vma-prior-to-folio-allocation +++ a/mm/hugetlb.c @@ -6261,6 +6261,12 @@ static vm_fault_t hugetlb_no_page(struct VM_UFFD_MISSING); }

+ if (!(vma->vm_flags & VM_MAYSHARE)) { + ret = vmf_anon_prepare(vmf); + if (unlikely(ret)) + goto out; + } + folio = alloc_hugetlb_folio(vma, haddr, 0); if (IS_ERR(folio)) { /* @@ -6297,15 +6303,12 @@ static vm_fault_t hugetlb_no_page(struct */ restore_reserve_on_error(h, vma, haddr, folio); folio_put(folio); + ret = VM_FAULT_SIGBUS; goto out; } new_pagecache_folio = true; } else { folio_lock(folio); - - ret = vmf_anon_prepare(vmf); - if (unlikely(ret)) - goto backout_unlocked; anon_rmap = 1; } } else { _

Patches currently in -mm which might be from vishal.moola@gmail.com are

hugetlb-check-for-anon_vma-prior-to-folio-allocation.patch hugetlb-convert-hugetlb_fault-to-use-struct-vm_fault.patch hugetlb-convert-hugetlb_no_page-to-use-struct-vm_fault.patch hugetlb-convert-hugetlb_no_page-to-use-struct-vm_fault-fix.patch hugetlb-convert-hugetlb_wp-to-use-struct-vm_fault.patch hugetlb-convert-hugetlb_wp-to-use-struct-vm_fault-fix.patch