CVE-2023-53630

In the Linux kernel, the following vulnerability has been resolved:

iommufd: Fix unpinning of pages when an access is present

syzkaller found that the calculation of batch_last_index should use

'start_index' since at input to this function the batch is either empty or

it has already been adjusted to cross any accesses so it will start at the

point we are unmapping from.

Getting this wrong causes the unmap to run over the end of the pages

which corrupts pages that were never mapped. In most cases this triggers

the num pinned debugging:

WARNING: CPU: 0 PID: 557 at drivers/iommu/iommufd/pages.c:294 __iopt_area_unfill_domain+0x152/0x560

Modules linked in:

CPU: 0 PID: 557 Comm: repro Not tainted 6.3.0-rc2-eeac8ede1755 #1

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

RIP: 0010:__iopt_area_unfill_domain+0x152/0x560

Code: d2 0f ff 44 8b 64 24 54 48 8b 44 24 48 31 ff 44 89 e6 48 89 44 24 38 e8 fc d3 0f ff 45 85 e4 0f 85 eb 01 00 00 e8 0e d2 0f ff <0f> 0b e8 07 d2 0f ff 48 8b 44 24 38 89 5c 24 58 89 18 8b 44 24 54

RSP: 0018:ffffc9000108baf0 EFLAGS: 00010246

RAX: 0000000000000000 RBX: 00000000ffffffff RCX: ffffffff821e3f85

RDX: 0000000000000000 RSI: ffff88800faf0000 RDI: 0000000000000002

RBP: ffffc9000108bd18 R08: 000000000003ca25 R09: 0000000000000014

R10: 000000000003ca00 R11: 0000000000000024 R12: 0000000000000004

R13: 0000000000000801 R14: 00000000000007ff R15: 0000000000000800

FS: 00007f3499ce1740(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000020000243 CR3: 00000000179c2001 CR4: 0000000000770ef0

PKRU: 55555554

Call Trace:

<TASK>

iopt_area_unfill_domain+0x32/0x40

iopt_table_remove_domain+0x23f/0x4c0

iommufd_device_selftest_detach+0x3a/0x90

iommufd_selftest_destroy+0x55/0x70

iommufd_object_destroy_user+0xce/0x130

iommufd_destroy+0xa2/0xc0

iommufd_fops_ioctl+0x206/0x330

__x64_sys_ioctl+0x10e/0x160

do_syscall_64+0x3b/0x90

entry_SYSCALL_64_after_hwframe+0x72/0xdc

Also add some useful WARN_ON sanity checks.