[syzbot] [iommu?] KMSAN: uninit-value in pfn_reader_next

[syzbot] [iommu?] KMSAN: uninit-value in pfn_reader_next

[syzbot]

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
=====================================================


---
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Re: [syzbot] [iommu?] KMSAN: uninit-value in pfn_reader_next

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in batch_from_domain

=====================================================
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_domain+0xe8c/0x1010 drivers/iommu/iommufd/pages.c:425
 batch_add_pfn_num drivers/iommu/iommufd/pages.c:365 [inline]
 batch_add_pfn drivers/iommu/iommufd/pages.c:398 [inline]
 batch_from_domain+0xe8c/0x1010 drivers/iommu/iommufd/pages.c:425
 iopt_area_unpin_domain drivers/iommu/iommufd/pages.c:1687 [inline]
 __iopt_area_unfill_domain+0xccf/0x1b90 drivers/iommu/iommufd/pages.c:1773
 iopt_area_unfill_domain+0x100/0x140 drivers/iommu/iommufd/pages.c:1828
 iopt_unfill_domain drivers/iommu/iommufd/io_pagetable.c:1025 [inline]
 iopt_table_remove_domain+0xada/0x1010 drivers/iommu/iommufd/io_pagetable.c:1269
 iommufd_hwpt_paging_destroy+0x21e/0x540 drivers/iommu/iommufd/hw_pagetable.c:30
 iommufd_object_remove+0x4c8/0x6c0 drivers/iommu/iommufd/main.c:273
 iommufd_object_put_and_try_destroy drivers/iommu/iommufd/iommufd_private.h:268 [inline]
 iommufd_hw_pagetable_put drivers/iommu/iommufd/iommufd_private.h:461 [inline]
 iommufd_hw_pagetable_detach+0x6e3/0xa10 drivers/iommu/iommufd/device.c:714
 iommufd_device_detach+0x38/0xe0 drivers/iommu/iommufd/device.c:1059
 iommufd_selftest_destroy+0x9e/0x100 drivers/iommu/iommufd/selftest.c:1951
 iommufd_fops_release+0x1e0/0x5f0 drivers/iommu/iommufd/main.c:361
 __fput+0x60e/0x1050 fs/file_table.c:468
 ____fput+0x25/0x30 fs/file_table.c:496
 task_work_run+0x208/0x2b0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0x2ff/0x1b20 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x1d7/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable batch created at:
 __iopt_area_unfill_domain+0xa8/0x1b90 drivers/iommu/iommufd/pages.c:1738
 iopt_area_unfill_domain+0x100/0x140 drivers/iommu/iommufd/pages.c:1828

CPU: 0 UID: 0 PID: 6581 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026
=====================================================


Tested on:

commit:         62085877 Merge tag 'kbuild-fixes-6.19-2' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1642c452580000
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=158cc452580000

Re: [syzbot] [iommu?] KMSAN: uninit-value in pfn_reader_next

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+df28076a30d726933015@syzkaller.appspotmail.com
Tested-by: syzbot+df28076a30d726933015@syzkaller.appspotmail.com

Tested on:

commit:         62085877 Merge tag 'kbuild-fixes-6.19-2' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1246bd22580000
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1007805a580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [iommu?] KMSAN: uninit-value in pfn_reader_next

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+df28076a30d726933015@syzkaller.appspotmail.com
Tested-by: syzbot+df28076a30d726933015@syzkaller.appspotmail.com

Tested on:

commit:         62085877 Merge tag 'kbuild-fixes-6.19-2' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12d13f9a580000
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11e6c452580000

Note: testing is done by a robot and is best-effort only.