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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rwUbP-0000000GbxN-28TT; Mon, 15 Apr 2024 22:15:03 +0000 Date: Mon, 15 Apr 2024 23:15:03 +0100 From: Matthew Wilcox To: Vishal Moola Cc: syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, muchun.song@linux.dev, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] KASAN: slab-use-after-free Read in __vma_reservation_common Message-ID: References: <000000000000daf1e10615e64dcb@google.com> <000000000000ae5d410615fea3bf@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2FDB54000B X-Stat-Signature: aanhuairc5ytr3nrtzfo5aa3u8sxq7pe X-HE-Tag: 1713219308-649381 X-HE-Meta: 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 D0A+XoTC OGs/zk8jZ/z0VGBiIpzuG5OObqQOMh2ke0POhOvIDPok9XNjh0XVOQ6Xiv0SxvbaOouyktMimxEHe32VGgWlHIlAh6AnP8+xcWDu422eMasARqbB0Umf7OS+06W/5hMqmP0/Jtp8E8nDkNtCvMrr5WlfMSWci9bsdPHg2hk85E1wPVqmSqeDJyxi1xHShzuvZS84iYRKRSG2TiOHX1Jy7d7u29E2SM0aH3vMD+1xFNuMmVBS6+iUB/NXdyxCwmVNGVMHexGZydawThn623gOMl2ETEdPxkfMduMHeP/l5V3h46zCf5UP7H2WTs+CveqFTRAa8lTGv3TlfVR9fsivbsH9BqE2PrRMv3ZZQnBuWuhVFSyWKQpN0Vye7Ug== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 15, 2024 at 03:05:44PM -0700, Vishal Moola wrote: > 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. But now you're calling vmf_anon_prepare() in the wrong place -- before we've determined that we need an anon folio. So we'll create an anon_vma even when we don't need one for this vma. This is definitely a pre-existing bug which you've exposed by making it happen more easily. Needs a different fix though.