From: Andrew Morton <akpm@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: kernel test robot <lkp@intel.com>,
Matt Porter <mporter@kernel.crashing.org>,
Alexandre Bounine <alex.bou9@gmail.com>,
Jing Xiangfeng <jingxiangfeng@huawei.com>,
Ira Weiny <ira.weiny@intel.com>,
John Hubbard <jhubbard@nvidia.com>,
Souptick Joarder <jrdr.linux@gmail.com>,
"Gustavo A . R . Silva" <gustavoars@kernel.org>,
Dan Carpenter <dan.carpenter@oracle.com>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] rapidio: Avoid bogus __alloc_size warning
Date: Thu, 9 Sep 2021 13:27:52 -0700 [thread overview]
Message-ID: <20210909132752.4bde36ccf50720e56160f00c@linux-foundation.org> (raw)
In-Reply-To: <20210909161409.2250920-1-keescook@chromium.org>
On Thu, 9 Sep 2021 09:14:09 -0700 Kees Cook <keescook@chromium.org> wrote:
> GCC 9.3 (but not later) incorrectly evaluates 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)))) {
That's an "error", not a warning. Or is this thanks to the new -Werror?
Either way, I'm inclined to cc:stable on this, because use of gcc-9 on
older kernels will be a common thing down the ages.
If it's really an "error" on non-Werror kernels then definitely cc:stable.
next prev parent reply other threads:[~2021-09-09 20:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 16:14 [PATCH] rapidio: Avoid bogus __alloc_size warning Kees Cook
2021-09-09 20:27 ` Andrew Morton [this message]
2021-09-09 22:26 ` John Hubbard
2021-09-09 22:51 ` Kees Cook
2021-09-09 23:11 ` Andrew Morton
2021-09-10 1:52 ` Kees Cook
2021-09-10 4:50 ` Dan Carpenter
2021-09-10 5:48 ` Andrew Morton
2021-09-10 6:29 ` Kees Cook
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