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AJvYcCUUk8smdqcGakvAtp41EWcDXHyuUmH71d3b2clGGzeT8/i/qCTOEV6zQiDIReWFQTCgDSchbHiUx2ooKvNpi4ktHYg= X-Gm-Message-State: AOJu0YwjLiavd74EMOijCq/bXaJ+zvK1t5Sw3gEnTTKyk2Ii1urUzNH3 2oVEQ+iU4JyKtP/TEVDuyq2QVX3wraDFxrOFLKpuY62bzuTjX4LI3NWQjKbOASc1JS4OyGo7NHU cnoFh9dmzFnUCuXT5w6EdjCOV4SpaReBvzRvU X-Google-Smtp-Source: AGHT+IEqBcJlc9hk11QYxUUW3Tt+HncgIEKlWgi7wAcHPn1nVS0sddMMhyd9YD1iPGbupGFNo8jCUcOQlDuC3ema1Aw= X-Received: by 2002:a17:906:168a:b0:a46:9985:b264 with SMTP id s10-20020a170906168a00b00a469985b264mr5879888ejd.62.1710796770210; Mon, 18 Mar 2024 14:19:30 -0700 (PDT) MIME-Version: 1.0 References: <000000000000bbb3d80613f243a6@google.com> <20240318210917.GA4210@cmpxchg.org> In-Reply-To: <20240318210917.GA4210@cmpxchg.org> From: Yosry Ahmed Date: Mon, 18 Mar 2024 14:18:51 -0700 Message-ID: Subject: Re: [syzbot] [mm?] kernel BUG in sg_init_one To: Johannes Weiner Cc: Nhat Pham , syzbot , akpm@linux-foundation.org, chengming.zhou@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Barry Song Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: E8FB2A0015 X-Rspam-User: X-Stat-Signature: gd9wb4d3m9k1fesox64odm96ipcojg1p X-Rspamd-Server: rspam03 X-HE-Tag: 1710796771-787077 X-HE-Meta: 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 HjXF4axr 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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: List-Subscribe: List-Unsubscribe: On Mon, Mar 18, 2024 at 2:09=E2=80=AFPM Johannes Weiner wrote: > > On Mon, Mar 18, 2024 at 01:17:19PM -0700, Yosry Ahmed wrote: > > On Mon, Mar 18, 2024 at 11:00=E2=80=AFAM Nhat Pham = wrote: > > > > > > On Mon, Mar 18, 2024 at 9:58=E2=80=AFAM syzbot > > > wrote: > > > > > > > > Hello, > > > > > > > > syzbot found the following issue on: > > > > > > > > HEAD commit: e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-= 09-36' .. > > > > git tree: upstream > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=3D13043ab= e180000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=3D19bb57c= 23dffc38e > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=3Dadbc983a1= 588b7805de3 > > > > compiler: arm-linux-gnueabi-gcc (Debian 12.2.0-14) 12.2.0, GN= U ld (GNU Binutils for Debian) 2.40 > > > > userspace arch: arm > > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D1706d= 231180000 > > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D13ba795= 9180000 > > > > > > > > Downloadable assets: > > > > disk image (non-bootable): https://storage.googleapis.com/syzbot-as= sets/8ead8862021c/non_bootable_disk-e5eb28f6.raw.xz > > > > vmlinux: https://storage.googleapis.com/syzbot-assets/0a7371c63ff2/= vmlinux-e5eb28f6.xz > > > > kernel image: https://storage.googleapis.com/syzbot-assets/7539441b= 4add/zImage-e5eb28f6.xz > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to th= e commit: > > > > Reported-by: syzbot+adbc983a1588b7805de3@syzkaller.appspotmail.com > > > > > > > > ------------[ cut here ]------------ > > > > kernel BUG at include/linux/scatterlist.h:187! > > > > > > Looks like the provided buffer is invalid: > > > > > > #ifdef CONFIG_DEBUG_SG > > > BUG_ON(!virt_addr_valid(buf)); > > > #endif > > > > > > which is "src" from: > > > > > > sg_init_one(&input, src, entry->length); > > > > > > Looking at the surrounding code and recent history, there's this > > > commit that stands out: > > > > > > mm/zswap: remove the memcpy if acomp is not sleepable > > > (sha: 270700dd06ca41a4779c19eb46608f076bb7d40e) > > > > > > which has the effect of, IIUC, using the zpool mapped memory directly > > > as src, instead of acomp_ctx->buffer (which was previously the case, > > > as zsmalloc was not sleepable). > > > > > > This might not necessarily be a bug with that commit itself, but migh= t > > > have revealed another bug elsewhere. > > > > > > Anyway, cc-ing the author, Barry Song, to fact check me :) Will take = a > > > closer look later. > > > > I am not a highmem expert, but the reproducer has CONFIG_HIGHMEM=3Dy, > > and it seems like zs_map_object() may return a highmem address if the > > compressed object is entirely in a single page to avoid copying to a > > buffer: > > > > if (off + class->size <=3D PAGE_SIZE) { > > /* this object is contained entirely within a page */ > > area->vm_addr =3D kmap_atomic(page); > > ret =3D area->vm_addr + off; > > goto out; > > } > > > > The virt_addr_valid() check seems to indicate that we expect a direct > > map address in sg_init_one(), right? > > If the page is highmem, kmap_atomic() establishes a temporary mapping > to it in the direct map, such that we have a legit kernel pointer to > the memory. Otherwise the memcpy() in zswap also wouldn't work... Am I > missing something? IIUC kmap_atomic() establishes a mapping in the kernel portion of the address space, but not a direct map mapping (i.e. not a linear mapping), right? Does virt_addr_valid() check for addresses being in the kernel portion of the address space, or it being a linear mapping? I thought it checks for the latter.