Re: [PATCH] iommufd: Protect against overflow of ALIGN() during iova allocation

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Aug 27, 2024 at 01:46:45PM -0300, Jason Gunthorpe wrote:
> Userspace can supply an iova and uptr such that the target iova alignment
> becomes really big and ALIGN() overflows which corrupts the selected area
> range during allocation. CONFIG_IOMMUFD_TEST can detect this:
> 
>    WARNING: CPU: 1 PID: 5092 at drivers/iommu/iommufd/io_pagetable.c:268 iopt_alloc_area_pages drivers/iommu/iommufd/io_pagetable.c:268 [inline]
>    WARNING: CPU: 1 PID: 5092 at drivers/iommu/iommufd/io_pagetable.c:268 iopt_map_pages+0xf95/0x1050 drivers/iommu/iommufd/io_pagetable.c:352
>    Modules linked in:
>    CPU: 1 PID: 5092 Comm: syz-executor294 Not tainted 6.10.0-rc5-syzkaller-00294-g3ffea9a7a6f7 #0
>    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
>    RIP: 0010:iopt_alloc_area_pages drivers/iommu/iommufd/io_pagetable.c:268 [inline]
>    RIP: 0010:iopt_map_pages+0xf95/0x1050 drivers/iommu/iommufd/io_pagetable.c:352
>    Code: fc e9 a4 f3 ff ff e8 1a 8b 4c fc 41 be e4 ff ff ff e9 8a f3 ff ff e8 0a 8b 4c fc 90 0f 0b 90 e9 37 f5 ff ff e8 fc 8a 4c fc 90 <0f> 0b 90 e9 68 f3 ff ff 48 c7 c1 ec 82 ad 8f 80 e1 07 80 c1 03 38
>    RSP: 0018:ffffc90003ebf9e0 EFLAGS: 00010293
>    RAX: ffffffff85499fa4 RBX: 00000000ffffffef RCX: ffff888079b49e00
>    RDX: 0000000000000000 RSI: 00000000ffffffef RDI: 0000000000000000
>    RBP: ffffc90003ebfc50 R08: ffffffff85499b30 R09: ffffffff85499942
>    R10: 0000000000000002 R11: ffff888079b49e00 R12: ffff8880228e0010
>    R13: 0000000000000000 R14: 1ffff920007d7f68 R15: ffffc90003ebfd00
>    FS:  000055557d760380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
>    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>    CR2: 00000000005fdeb8 CR3: 000000007404a000 CR4: 00000000003506f0
>    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>    Call Trace:
>     <TASK>
>     iommufd_ioas_copy+0x610/0x7b0 drivers/iommu/iommufd/ioas.c:274
>     iommufd_fops_ioctl+0x4d9/0x5a0 drivers/iommu/iommufd/main.c:421
>     vfs_ioctl fs/ioctl.c:51 [inline]
>     __do_sys_ioctl fs/ioctl.c:907 [inline]
>     __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
>     do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>     do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>     entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Cap the automatic alignment to the huge page size, which is probably a
> better idea overall. Huge automatic alignments can fragment and chew up
> the available IOVA space without any reason.
> 
> Cc: stable@vger.kernel.org
> Fixes: 51fe6141f0f6 ("iommufd: Data structure to provide IOVA to PFN mapping")
> Reported-by: syzbot+16073ebbc4c64b819b47@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/r/000000000000388410061a74f014@google.com
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/iommu/iommufd/io_pagetable.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Applied to for-next

Thanks,
Jason