Jason has been running Syzkaller that 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.
Fixes: 9227da7816dd ("iommufd: Add iommufd_access_change_ioas(_id) helpers") Cc: stable@vger.kernel.org Reported-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com --- drivers/iommu/iommufd/selftest.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c index 2bfe77bd351d..d59e199a8705 100644 --- a/drivers/iommu/iommufd/selftest.c +++ b/drivers/iommu/iommufd/selftest.c @@ -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)