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AJvYcCXFmp0lLH/nW8NWORkVgO+TC338AvwWFdK48QzOpFZ833F4zWEn8E8AfwoG8iG1/r7n1FiXYO0RTg==@kvack.org X-Gm-Message-State: AOJu0YxZXCb4nl7btwdEC+BOmGzfSd1fGaXJci0Pa9rh19V7LI4ydz9N KFV4Mry/xHW2SDQKdilkUMQsKq8pXavrgDVXe3B7GU6ymKNtynNVPX8KJtdPgy3cWjsDlJMQmNR IOOjws8/5rl/Tu7ZtX9vNeSXva80ZkGo= X-Gm-Gg: AY/fxX4Xyze/Xe9QVl2N9ng9STd1RwbSwMtJbTb09gfpuw3oPgqLFUYaK7ZrPXXh9yb HnKmuZI59aBl0RqrLqn97p+mhwaUZI3f/GSDwYfb8WTascR6Fh+b8qQuRbRyacTfDu4Q+4Ss6Bl A+h7/gz63hMgCSuPzOhuATCOCIrhVdBhSp8qrbNb73vd5cjG2aPMi4mVEc47HZrMFx+M38eJTHe Km37ozsiDRCQaLdJzX6FO0n/MmA8rd5V8yk+K2LhgqNeDhMmW22sdLououer1+T5dcRMg== X-Google-Smtp-Source: AGHT+IE938wNEPaLZPltBzdnAMsfztao26G/+Iic5HapTSkvMaU6IBZ1rUfupGogiF0ZOIc5PKvZCRFAe0EiDMuvhco= X-Received: by 2002:ad4:5c68:0:b0:87c:2360:d404 with SMTP id 6a1803df08f44-88d81278b01mr272517186d6.7.1766530015663; Tue, 23 Dec 2025 14:46:55 -0800 (PST) MIME-Version: 1.0 References: <6949370f.050a0220.1b4e0c.0038.GAE@google.com> In-Reply-To: <6949370f.050a0220.1b4e0c.0038.GAE@google.com> From: Barry Song <21cnbao@gmail.com> Date: Wed, 24 Dec 2025 11:46:44 +1300 X-Gm-Features: AQt7F2qilzp3GLkZFHYyCCu7gukfo6SnbVeg6EJzZG1zTeLzCjcD_xzeRleg49A Message-ID: Subject: Re: [syzbot] [mm?] KMSAN: uninit-value in swap_writeout To: syzbot , Baolin Wang , Hugh Dickins Cc: akpm@linux-foundation.org, bhe@redhat.com, chrisl@kernel.org, kasong@tencent.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: CB5A21C000F X-Rspamd-Server: rspam10 X-Stat-Signature: he4e9gymj4k5akkqi4dnmcngym4mxmd3 X-HE-Tag: 1766530016-652130 X-HE-Meta: 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 Pn8TTf2W uWxsj8cbjyNDSU8CsNp3d+YIZpje2//4KgdJiW77Vz1h80AT22lQyJTpB57ZNJXDXJ7k8UyP83nkybTzWS7tKBc5bInKSLi4DdW4+vVyA4fWnteizwWXZ9myHJgyn3eXCQNIJdG72eoVuJpL2c0O33aESR0mmdPoNWRXShohncrE1LeokUG80aAfDcpsf/hw9PCLUiqaTdH9P9mT5t7Ioj4h8eYhnSFNDlJ6PRh/lR7/1SUdb5x05KpYQN+WtfYnJhTHpyk3N1hG1NkEhhR0BIW+MzUYPkFRAII05kEU1wp9mOZPOsCgR26TheoB+SSJDndbSe0ksspKPuJLV+lHYPb5D21M6fRaTOiIHxI9PjQSpyFbYIhq1M7WAAZ0cNzgOaIBLVzAo0GG5tMEgy8MtiE7jH+bwMlxAFdZbiMeOZAjDziM2D/tWTgL7CXylsux1sWO49gtScr5XLp8Nlk2tGYYIVLGsSjMtFlKR5eBjgRNtcmtxXQaAKT4evwutwFNjkKIGUIsU0FgDrJrTF7Bh1nIUT9FWreuIuHiN 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: > > Uninit was created at: > __alloc_frozen_pages_noprof+0x421/0xab0 mm/page_alloc.c:5233 > alloc_pages_mpol+0x328/0x860 mm/mempolicy.c:2486 > folio_alloc_mpol_noprof+0x56/0x1d0 mm/mempolicy.c:2505 > shmem_alloc_folio mm/shmem.c:1890 [inline] > shmem_alloc_and_add_folio+0xc56/0x1bd0 mm/shmem.c:1932 > shmem_get_folio_gfp+0xad3/0x1fc0 mm/shmem.c:2556 > shmem_get_folio mm/shmem.c:2662 [inline] > shmem_symlink+0x562/0xad0 mm/shmem.c:4129 > vfs_symlink+0x42f/0x4c0 fs/namei.c:5514 > do_symlinkat+0x2ae/0xbb0 fs/namei.c:5541 +Hugh and Baolin. This happens in the shmem symlink path, where newly allocated folios are not cleared for some reason. As a result, is_folio_zero_filled() ends up reading uninitialized data. Clearing newly allocated folios in shmem_get_folio_gfp() would fix the issue, but it may not be the proper solution. We will need Hugh and Baolin=E2=80=99s guidance to recommend an appropriate fix. > __do_sys_symlinkat fs/namei.c:5562 [inline] > __se_sys_symlinkat fs/namei.c:5559 [inline] > __ia32_sys_symlinkat+0xf5/0x180 fs/namei.c:5559 > ia32_sys_call+0x385e/0x4340 arch/x86/include/generated/asm/syscalls_32.h= :305 > do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] > __do_fast_syscall_32+0x15a/0x330 arch/x86/entry/syscall_32.c:307 > do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:332 > do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:370 > entry_SYSENTER_compat_after_hwframe+0x84/0x8e > > CPU: 0 UID: 0 PID: 7862 Comm: syz.2.517 Tainted: G L syz= kaller #0 PREEMPT(none) > Tainted: [L]=3DSOFTLOCKUP > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS G= oogle 10/25/2025 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D Thanks Barry