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* [PATCH] iommufd: Protect against overflow of ALIGN() during iova allocation
@ 2024-08-27 16:46 Jason Gunthorpe
  2024-08-27 17:46 ` Nicolin Chen
  2024-09-05 19:03 ` Jason Gunthorpe
  0 siblings, 2 replies; 3+ messages in thread
From: Jason Gunthorpe @ 2024-08-27 16:46 UTC (permalink / raw)
  To: iommu, Joerg Roedel
  Cc: Kevin Tian, Lixiao Yang, Matthew Rosato, Nicolin Chen, patches,
	syzbot+16073ebbc4c64b819b47, Yi Liu

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(+)

diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c
index bbbc8a044bcf7f..4bf7ccd39d465c 100644
--- a/drivers/iommu/iommufd/io_pagetable.c
+++ b/drivers/iommu/iommufd/io_pagetable.c
@@ -112,6 +112,7 @@ static int iopt_alloc_iova(struct io_pagetable *iopt, unsigned long *iova,
 	unsigned long page_offset = uptr % PAGE_SIZE;
 	struct interval_tree_double_span_iter used_span;
 	struct interval_tree_span_iter allowed_span;
+	unsigned long max_alignment = PAGE_SIZE;
 	unsigned long iova_alignment;
 
 	lockdep_assert_held(&iopt->iova_rwsem);
@@ -131,6 +132,13 @@ static int iopt_alloc_iova(struct io_pagetable *iopt, unsigned long *iova,
 				       roundup_pow_of_two(length),
 				       1UL << __ffs64(uptr));
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	max_alignment = HPAGE_SIZE;
+#endif
+	/* Protect against ALIGN() overflow */
+	if (iova_alignment >= max_alignment)
+		iova_alignment = max_alignment;
+
 	if (iova_alignment < iopt->iova_alignment)
 		return -EINVAL;
 

base-commit: 76889bbaabf5cab981a74ed69cb3816921edc5d4
-- 
2.46.0


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2024-08-27 16:46 [PATCH] iommufd: Protect against overflow of ALIGN() during iova allocation Jason Gunthorpe
2024-08-27 17:46 ` Nicolin Chen
2024-09-05 19:03 ` Jason Gunthorpe

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