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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qP64A-007mFk-Is; Thu, 27 Jul 2023 18:50:26 +0000 Date: Thu, 27 Jul 2023 19:50:26 +0100 From: Matthew Wilcox To: syzbot Cc: akpm@linux-foundation.org, liam.howlett@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] WARNING: suspicious RCU usage in mas_walk (2) Message-ID: References: <000000000000607ff905ffc8e477@google.com> <0000000000000aeb7f06015e5cbd@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000000000000aeb7f06015e5cbd@google.com> X-Stat-Signature: hyy9e3s9ghmg9z47ij5rd9hx7mqeen3q X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C520240029 X-Rspam-User: X-HE-Tag: 1690483832-175619 X-HE-Meta: U2FsdGVkX195af/pIWAqtuRAg+AczPW2gUblSvOsfh1QYD8cAS+jKnjwMa6c2nYL0G35lMOvaMOuKDhMK+OCoG0+iKcnlIs0kM64E7JInhZ30qxBsYqMD35CiH48ZgNv2gkQqwmFjO1uK0LQ57JIbZONiQlPgnlHZV9PPWyfnxpH+EV2ORrypL4RSp3f+nlfikh5JS2Rljna4xo3HE8rge/7rjxmrqE+fLH0PmEkNody3dj+vhC5+zKFg3mu8YwOR3eA6JNButwXCR08A1JMkV4r3siNkmP+honO5fgFF5fpkJXSxAur9FXh8BxIMHyM9Qkfedr6cY3S9UmXOC9/IQda29pJIakAt+hIQdzcuqfT2ffX/ulDHCuMoD5vUGz74AQ56siSnYiqtdn40RFZ5wWuAHFvkCs7Kvp5LGE1J4G6xf9a7UB4aNlkppAAmTS03fIjiPW7APLh11u8zkofboh3tkEF+Kle6huV1K7ow1DBL/jrmJqw5hRyvM+SbjHjHG19p97IYQGFkVE5UI2tddzQW1EO9BEioG0OkHulhTyd4eAq8irrnXsL75zp0a9pMriaYeucfkxtKbGEn0/boxfvbP0T3UMqFdHpe5fw7TkFKDg0LVuZP1nnt1KAnvWnN2FYFhuMcRP+GSn4Vz9k3L0d/GPoEomjnX0L9Z6EvzD8RtF6t9X0OTDlQZOtwNjvB7HHG2XiE5swrI2GMt/GxFy0YUsH7V4BwtmjECvDNl+lCF+BYgGJwq2XEYEPL5I02vffUZrrxYTSiO94IjQpzjZobFrXLugAnRq+bV0UlqrerCAwQbBY0MB4wuYZL+vm5gqm3RhuxOYTv+PpyUto2i6rMisUTA8mCy84Zzw0OI9e2VeZiv3JjRIBdszJERVKf8+/yHkxoKF3JZ7hr4tMMitbq8tOsVlpUhMCLdpKIXiEB7KhVUJ6nwRWpFDudB1ZxvVtx633W00bzqr8Y9Z ZyfbKBkN 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 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: On Tue, Jul 25, 2023 at 11:57:22PM -0700, syzbot wrote: > syzbot has bisected this issue to: FWIW, this is unrelated to the previous issue. It's the caller of mas_walk() that has violated the locking constraints, and mas_walk() is simply reporting the issue. Is there a way to get syzbot to understand that it needs to unwind the call-stack further to decide who to blame? > commit a52f58b34afe095ebc5823684eb264404dad6f7b > Author: Matthew Wilcox (Oracle) > Date: Mon Jul 24 18:54:10 2023 +0000 > > mm: handle faults that merely update the accessed bit under the VMA lock > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1783585ea80000 > start commit: [unknown] > git tree: linux-next > final oops: https://syzkaller.appspot.com/x/report.txt?x=1443585ea80000 > console output: https://syzkaller.appspot.com/x/log.txt?x=1043585ea80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=f481ab36ce878b84 > dashboard link: https://syzkaller.appspot.com/bug?extid=8645fe63c4d22c8d27b8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1697cec9a80000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1566986ea80000 #syz test diff --git a/mm/memory.c b/mm/memory.c index 20a2e9ed4aeb..57b271108bdc 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3567,6 +3567,12 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) return 0; } copy: + if ((vmf->flags & FAULT_FLAG_VMA_LOCK) && !vma->anon_vma) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + vma_end_read(vmf->vma); + return VM_FAULT_RETRY; + } + /* * Ok, we need to copy. Oh, well.. */