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iommufd: Fix protection fault in iommufd_test_syz_conv_iova

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Syzkaller reported the following bug:

  general protection fault, probably for non-canonical address 0xdffffc0000000038: 0000 [#1] SMP KASAN
  KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7]
  Call Trace:
   lock_acquire
   lock_acquire+0x1ce/0x4f0
   down_read+0x93/0x4a0
   iommufd_test_syz_conv_iova+0x56/0x1f0
   iommufd_test_access_rw.isra.0+0x2ec/0x390
   iommufd_test+0x1058/0x1e30
   iommufd_fops_ioctl+0x381/0x510
   vfs_ioctl
   __do_sys_ioctl
   __se_sys_ioctl
   __x64_sys_ioctl+0x170/0x1e0
   do_syscall_x64
   do_syscall_64+0x71/0x140

This is because the new iommufd_access_change_ioas() sets access->ioas to
NULL during its process, so the lock might be gone in a concurrent racing
context.

Fix this by doing the same access->ioas sanity as iommufd_access_rw() and
iommufd_access_pin_pages() functions do.

Cc: stable@vger.kernel.org
Fixes: 9227da7816 ("iommufd: Add iommufd_access_change_ioas(_id) helpers")
Link: https://lore.kernel.org/r/3f1932acaf1dd494d404c04364d73ce8f57f3e5e.1708636627.git.nicolinc@nvidia.com
Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Nicolin Chen 2024-02-22 13:23:47 -08:00 committed by Jason Gunthorpe
parent fde372df96
commit cf7c278982
1 changed files with 21 additions and 6 deletions
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27
drivers/iommu/iommufd/selftest.c
View file

@ -63,8 +63,8 @@ enum {
* In syzkaller mode the 64 bit IOVA is converted into an nth area and offset
* value. This has a much smaller randomization space and syzkaller can hit it.
*/
static unsigned long iommufd_test_syz_conv_iova(struct io_pagetable *iopt,
u64 *iova)
static unsigned long __iommufd_test_syz_conv_iova(struct io_pagetable *iopt,
u64 *iova)
{
struct syz_layout {
__u32 nth_area;
@ -88,6 +88,21 @@ static unsigned long iommufd_test_syz_conv_iova(struct io_pagetable *iopt,
return 0;
}
static unsigned long iommufd_test_syz_conv_iova(struct iommufd_access *access,
u64 *iova)
{
unsigned long ret;
mutex_lock(&access->ioas_lock);
if (!access->ioas) {
mutex_unlock(&access->ioas_lock);
return 0;
}
ret = __iommufd_test_syz_conv_iova(&access->ioas->iopt, iova);
mutex_unlock(&access->ioas_lock);
return ret;
}
void iommufd_test_syz_conv_iova_id(struct iommufd_ucmd *ucmd,
unsigned int ioas_id, u64 *iova, u32 *flags)
{
@ -100,7 +115,7 @@ void iommufd_test_syz_conv_iova_id(struct iommufd_ucmd *ucmd,
ioas = iommufd_get_ioas(ucmd->ictx, ioas_id);
if (IS_ERR(ioas))
return;
*iova = iommufd_test_syz_conv_iova(&ioas->iopt, iova);
*iova = __iommufd_test_syz_conv_iova(&ioas->iopt, iova);
iommufd_put_object(ucmd->ictx, &ioas->obj);
}
@ -1161,7 +1176,7 @@ static int iommufd_test_access_pages(struct iommufd_ucmd *ucmd,
}
if (flags & MOCK_FLAGS_ACCESS_SYZ)
iova = iommufd_test_syz_conv_iova(&staccess->access->ioas->iopt,
iova = iommufd_test_syz_conv_iova(staccess->access,
&cmd->access_pages.iova);
npages = (ALIGN(iova + length, PAGE_SIZE) -
@ -1263,8 +1278,8 @@ static int iommufd_test_access_rw(struct iommufd_ucmd *ucmd,
}
if (flags & MOCK_FLAGS_ACCESS_SYZ)
iova = iommufd_test_syz_conv_iova(&staccess->access->ioas->iopt,
&cmd->access_rw.iova);
iova = iommufd_test_syz_conv_iova(staccess->access,
&cmd->access_rw.iova);
rc = iommufd_access_rw(staccess->access, iova, tmp, length, flags);
if (rc)