[PATCH 6.7 112/162] iommufd: Fix protection fault in iommufd_test_syz_conv_iova

Greg Kroah-Hartman
2024-03-04T21:30:47Z

From: Nicolin Chen <nicolinc@nvidia.com>

commit cf7c2789822db8b5efa34f5ebcf1621bc0008d48 upstream.

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: 9227da7816dd ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iommu/iommufd/selftest.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)

--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -48,8 +48,8 @@ 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;
@@ -73,6 +73,21 @@ static unsigned long iommufd_test_syz_co
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)
{
@@ -85,7 +100,7 @@ void iommufd_test_syz_conv_iova_id(struc
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);
}

@@ -1045,7 +1060,7 @@ static int iommufd_test_access_pages(str
}

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) -
@@ -1147,8 +1162,8 @@ static int iommufd_test_access_rw(struct
}

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)