Re: [PATCH v3 1/8] rapidio: Avoid bogus __alloc_size warning
From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Date: 2021-09-30 22:42:01
Also in:
linux-hardening, linux-kbuild, lkml
On Thu, Sep 30, 2021 at 03:26:57PM -0700, Kees Cook wrote:
After adding __alloc_size attributes to the allocators, GCC 9.3 (but not
later) may incorrectly evaluate the arguments to check_copy_size(),
getting seemingly confused by the size being returned from array_size().
Instead, perform the calculation once, which both makes the code more
readable and avoids the bug in GCC.
In file included from arch/x86/include/asm/preempt.h:7,
from include/linux/preempt.h:78,
from include/linux/spinlock.h:55,
from include/linux/mm_types.h:9,
from include/linux/buildid.h:5,
from include/linux/module.h:14,
from drivers/rapidio/devices/rio_mport_cdev.c:13:
In function 'check_copy_size',
inlined from 'copy_from_user' at include/linux/uaccess.h:191:6,
inlined from 'rio_mport_transfer_ioctl' at drivers/rapidio/devices/rio_mport_cdev.c:983:6:
include/linux/thread_info.h:213:4: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small
213 | __bad_copy_to();
| ^~~~~~~~~~~~~~~
But the allocation size and the copy size are identical:
transfer = vmalloc(array_size(sizeof(*transfer), transaction.count));
if (!transfer)
return -ENOMEM;
if (unlikely(copy_from_user(transfer,
(void __user *)(uintptr_t)transaction.block,
array_size(sizeof(*transfer), transaction.count)))) {
Reported-by: kernel test robot <redacted>
Link: https://lore.kernel.org/linux-mm/202109091134.FHnRmRxu-lkp@intel.com/ (local)
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Alexandre Bounine <alex.bou9@gmail.com>
Cc: Jing Xiangfeng <redacted>
Cc: Ira Weiny <redacted>
Cc: Souptick Joarder <redacted>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kees Cook <redacted>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Thanks -- Gustavo
quoted hunk ↗ jump to hunk
--- drivers/rapidio/devices/rio_mport_cdev.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c index 94331d999d27..7df466e22282 100644 --- a/drivers/rapidio/devices/rio_mport_cdev.c +++ b/drivers/rapidio/devices/rio_mport_cdev.c@@ -965,6 +965,7 @@ static int rio_mport_transfer_ioctl(struct file *filp, void __user *arg) struct rio_transfer_io *transfer; enum dma_data_direction dir; int i, ret = 0; + size_t size; if (unlikely(copy_from_user(&transaction, arg, sizeof(transaction)))) return -EFAULT;@@ -976,13 +977,14 @@ static int rio_mport_transfer_ioctl(struct file *filp, void __user *arg) priv->md->properties.transfer_mode) == 0) return -ENODEV; - transfer = vmalloc(array_size(sizeof(*transfer), transaction.count)); + size = array_size(sizeof(*transfer), transaction.count); + transfer = vmalloc(size); if (!transfer) return -ENOMEM; if (unlikely(copy_from_user(transfer, (void __user *)(uintptr_t)transaction.block, - array_size(sizeof(*transfer), transaction.count)))) { + size))) { ret = -EFAULT; goto out_free; }@@ -994,8 +996,7 @@ static int rio_mport_transfer_ioctl(struct file *filp, void __user *arg) transaction.sync, dir, &transfer[i]); if (unlikely(copy_to_user((void __user *)(uintptr_t)transaction.block, - transfer, - array_size(sizeof(*transfer), transaction.count)))) + transfer, size))) ret = -EFAULT; out_free:-- 2.30.2