6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Vishal Moola (Oracle) vishal.moola@gmail.com
commit 2a058ab3286d6475b2082b90c2d2182d2fea4b39 upstream.
Some callers of vmf_anon_prepare() may not want us to release the per-VMA lock ourselves. Rename vmf_anon_prepare() to __vmf_anon_prepare() and let the callers drop the lock when desired.
Also, make vmf_anon_prepare() a wrapper that releases the per-VMA lock itself for any callers that don't care.
This is in preparation to fix this bug reported by syzbot: https://lore.kernel.org/linux-mm/00000000000067c20b06219fbc26@google.com/
Link: https://lkml.kernel.org/r/20240914194243.245-1-vishal.moola@gmail.com Fixes: 9acad7ba3e25 ("hugetlb: use vmf_anon_prepare() instead of anon_vma_prepare()") Reported-by: syzbot+2dab93857ee95f2eeb08@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-mm/00000000000067c20b06219fbc26@google.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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/internal.h | 11 ++++++++++- mm/memory.c | 8 +++----- 2 files changed, 13 insertions(+), 6 deletions(-)
--- a/mm/internal.h +++ b/mm/internal.h @@ -293,7 +293,16 @@ static inline void wake_throttle_isolate wake_up(wqh); }
-vm_fault_t vmf_anon_prepare(struct vm_fault *vmf); +vm_fault_t __vmf_anon_prepare(struct vm_fault *vmf); +static inline vm_fault_t vmf_anon_prepare(struct vm_fault *vmf) +{ + vm_fault_t ret = __vmf_anon_prepare(vmf); + + if (unlikely(ret & VM_FAULT_RETRY)) + vma_end_read(vmf->vma); + return ret; +} + vm_fault_t do_swap_page(struct vm_fault *vmf); void folio_rotate_reclaimable(struct folio *folio); bool __folio_end_writeback(struct folio *folio); --- a/mm/memory.c +++ b/mm/memory.c @@ -3226,7 +3226,7 @@ static inline vm_fault_t vmf_can_call_fa }
/** - * vmf_anon_prepare - Prepare to handle an anonymous fault. + * __vmf_anon_prepare - Prepare to handle an anonymous fault. * @vmf: The vm_fault descriptor passed from the fault handler. * * When preparing to insert an anonymous page into a VMA from a @@ -3240,7 +3240,7 @@ static inline vm_fault_t vmf_can_call_fa * Return: 0 if fault handling can proceed. Any other value should be * returned to the caller. */ -vm_fault_t vmf_anon_prepare(struct vm_fault *vmf) +vm_fault_t __vmf_anon_prepare(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; vm_fault_t ret = 0; @@ -3248,10 +3248,8 @@ vm_fault_t vmf_anon_prepare(struct vm_fa if (likely(vma->anon_vma)) return 0; if (vmf->flags & FAULT_FLAG_VMA_LOCK) { - if (!mmap_read_trylock(vma->vm_mm)) { - vma_end_read(vma); + if (!mmap_read_trylock(vma->vm_mm)) return VM_FAULT_RETRY; - } } if (__anon_vma_prepare(vma)) ret = VM_FAULT_OOM;