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Fri, 23 Jan 2026 22:45:26 -0800 (PST) Date: Fri, 23 Jan 2026 22:45:26 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69746a86.050a0220.226181.0002.GAE@google.com> Subject: [syzbot] [iommu?] KMSAN: uninit-value in pfn_reader_next From: syzbot To: iommu@lists.linux.dev, jgg@ziepe.ca, joro@8bytes.org, kevin.tian@intel.com, linux-kernel@vger.kernel.org, robin.murphy@arm.com, syzkaller-bugs@googlegroups.com, will@kernel.org Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: c072629f05d7 Merge tag 'v6.19-p4' of git://git.kernel.org/.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1716005a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8bf02b9e495b9fcd dashboard link: https://syzkaller.appspot.com/bug?extid=df28076a30d726933015 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1436b79a580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15a63d22580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/b6b938ba4a72/disk-c072629f.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/bb1384b011b2/vmlinux-c072629f.xz kernel image: https://storage.googleapis.com/syzbot-assets/1dd4bb2f206e/bzImage-c072629f.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+df28076a30d726933015@syzkaller.appspotmail.com iommufd_mock iommufd_mock0: Adding to iommu group 0 ===================================================== BUG: KMSAN: uninit-value in batch_add_pfn_num drivers/iommu/iommufd/pages.c:365 [inline] BUG: KMSAN: uninit-value in batch_add_pfn drivers/iommu/iommufd/pages.c:398 [inline] BUG: KMSAN: uninit-value in batch_from_pages drivers/iommu/iommufd/pages.c:658 [inline] BUG: KMSAN: uninit-value in pfn_reader_fill_span drivers/iommu/iommufd/pages.c:1220 [inline] BUG: KMSAN: uninit-value in pfn_reader_next+0x1d5a/0x3e50 drivers/iommu/iommufd/pages.c:1247 batch_add_pfn_num drivers/iommu/iommufd/pages.c:365 [inline] batch_add_pfn drivers/iommu/iommufd/pages.c:398 [inline] batch_from_pages drivers/iommu/iommufd/pages.c:658 [inline] pfn_reader_fill_span drivers/iommu/iommufd/pages.c:1220 [inline] pfn_reader_next+0x1d5a/0x3e50 drivers/iommu/iommufd/pages.c:1247 pfn_reader_first+0xbcf/0xee0 drivers/iommu/iommufd/pages.c:1354 iopt_area_fill_domains+0x202/0x1590 drivers/iommu/iommufd/pages.c:1917 iopt_fill_domains_pages drivers/iommu/iommufd/io_pagetable.c:359 [inline] iopt_map_pages+0x1ba5/0x2130 drivers/iommu/iommufd/io_pagetable.c:387 iopt_map_common+0x224/0x610 drivers/iommu/iommufd/io_pagetable.c:425 iopt_map_user_pages+0x148/0x1c0 drivers/iommu/iommufd/io_pagetable.c:466 iommufd_ioas_map+0x6a2/0x9b0 drivers/iommu/iommufd/ioas.c:270 iommufd_fops_ioctl+0x82a/0x9e0 drivers/iommu/iommufd/main.c:533 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0x23c/0x400 fs/ioctl.c:583 __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:583 x64_sys_call+0x18a7/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Local variable pfns created at: iopt_area_fill_domains+0x5c/0x1590 drivers/iommu/iommufd/pages.c:1900 iopt_fill_domains_pages drivers/iommu/iommufd/io_pagetable.c:359 [inline] iopt_map_pages+0x1ba5/0x2130 drivers/iommu/iommufd/io_pagetable.c:387 CPU: 0 UID: 0 PID: 6065 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(voluntary) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026 ===================================================== --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup