Messages in this thread | | | Date | Thu, 9 Sep 2021 13:27:52 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] rapidio: Avoid bogus __alloc_size warning |
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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.
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