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/hugetlb-check-for-anon_vma-prior-to-folio-allocation.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: "Vishal Moola (Oracle)" <vishal.moola@xxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxx 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
