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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , Davidlohr Bueso , SJ Park , Kees Cook , Colin Cross Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Lorenzo Stoakes (ARM)" , stable@vger.kernel.org X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=2019; i=ljs@kernel.org; h=from:subject:message-id; bh=pBDKonRJs5TA7YWHg4RHbXCo1gcPUiIEkJW4rM9Bgss=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLJup7ZwnTcrklmpLv+v7b5ZTk5rgu3W38Kusn8WXX+/P +DA96yYjlIWBjEuBlkxRZbnX8T3B4mEzeu84O8GM4eVCWQIAxenAEzk52GGvwI27BPt4hz1fVt+ GIvef1ex+25XdOuMn8UV36YvjTrWIM7I8NIhpL7vNP/EEvbTHnKC/83mnWg2v2t7j23qWYOY0zu XcAAA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 91249140009 X-Stat-Signature: 3y1muxyyysgbckb465ug1t73joi36xu5 X-Rspam-User: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1792763282-13047 X-HE-Meta: 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 cln6GSmB ipi4pKVO0oipv677ZH4vPYcTKbDWSLVPb+2Rt3QeP1e0zSlIqBC6Cp+1b/cummAFeHW/IxFTTRik3tKaR+tMxR1MMNiwDcbjPUfjC1aKTQ/A+yTmh+meIiwLbOIneMuwzCrYmYIgOwT0+Z7pyYFXXY6gAYFy5jmpDoFZfSzMyMofHWA97qlUqwCUMOHW/Q3DDPrKWUY+5bS0JNB+qkxTMEwZOUqsCIqxc2Ig+To5DergI1T7+wQtexqKpVitCt2829NCWawrdWZ+xv2DMV94woPjMpvRIlfpZJULU1Md6rDxg7VXduAwAByse2OJYoyO/HruUQ2DL9a88CvQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 From: "David Hildenbrand (Arm)" __split_vma() duplicates the source VMA before taking its VMA write lock, and until the VMA is write-locked, a concurrent thread might set VMA_MAYBE_GUARD_BIT, resulting in the duplication missing the flag. If this happens, then fork may fail to duplicate guard markers and, if a file-backed mapping, THP collapse may also discard the markers. Resolve this by taking the VMA write lock before vm_area_dup() and, since all callers of vm_area_dup() now hold the VMA write lock, assert that this is the case there, and add a comment to explain why it's needed. Fixes: 2ab7f1bbafc9 ("mm/madvise: allow guard page install/remove under VMA lock") Cc: Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (ARM) [ ljs - add VMA write assert in vm_area_dup(), commit message touchup ] Signed-off-by: Lorenzo Stoakes (ARM) --- mm/vma.c | 2 +- mm/vma_init.c | 3 +++ 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/vma.c b/mm/vma.c index 1be613044b4a..aa59005e2f42 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -538,6 +538,7 @@ __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, return err; } + vma_start_write(vma); new = vm_area_dup(vma); if (!new) return -ENOMEM; @@ -568,7 +569,6 @@ __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, if (new->vm_ops && new->vm_ops->open) new->vm_ops->open(new); - vma_start_write(vma); vma_start_write(new); init_vma_prep(&vp, vma); diff --git a/mm/vma_init.c b/mm/vma_init.c index baa7e82f47e3..d661f229a734 100644 --- a/mm/vma_init.c +++ b/mm/vma_init.c @@ -127,6 +127,9 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) { struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); + /* Must hold a write lock to stabilise atomic VMA flags. */ + vma_assert_write_locked(orig); + if (!new) return NULL; -- 2.56.0