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hugetlb: check for anon_vma prior to folio allocation 

Commit 9acad7ba3e ("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: 9acad7ba3e ("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>
This commit is contained in:
Vishal Moola (Oracle) 2024-04-15 14:17:47 -07:00 committed by Andrew Morton
parent 682886ec69
commit 37641efaa3
1 changed files with 7 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
mm/hugetlb.c
View File

@ -6261,6 +6261,12 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
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 mm_struct *mm,
*/
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 {