Hi Ilya,
On 8/14/24 14:09, Simon Horman wrote:
> On Wed, Aug 14, 2024 at 12:35:28PM +0200, Ilya Maximets wrote:
>> memcpy() is allowed to make alignment assumptions based on the argument
>> type. We have to cast before using it to avoid misaligned reads:
I guess that's fine. But I'm not sure I understand how memcpy() is
allowed to make any assumption based on the argument type. Isn't
memcpy() supposed to be a function call?
At least the man page on my machine says:
NAME
memcpy - copy memory area
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <string.h>
void *memcpy(void dest[restrict .n], const void src[restrict .n],
size_t n);
Is it actually the compiler doing some special magic behind the scenes?
>>
>> lib/netdev-linux.c:6738:41: runtime error: load of misaligned address
>> 0x51b000008db4 for type 'const struct rpl_rtnl_link_stats64 *',
>> which requires 8 byte alignment
>> 0x51b000008db4: note: pointer points here
>> cc 00 17 00 01 00 00 00 00 00 00 00 01 00 00 00
>> ^
>> 0 0xad2d8 in get_stats_via_netlink lib/netdev-linux.c:6738:17
>> 1 0x9dcce in netdev_linux_get_stats lib/netdev-linux.c:2293:13
>> 2 0xee5b8 in netdev_get_stats lib/netdev.c:1722:16
>> 3 0xc07ad in iface_refresh_stats vswitchd/bridge.c:2795:5
>> 4 0xbf4fc in iface_create vswitchd/bridge.c:2274:5
>> 5 0xbf4fc in bridge_add_ports__ vswitchd/bridge.c:1225:21
>> 6 0x989fc in bridge_add_ports vswitchd/bridge.c:1236:5
>> 7 0x989fc in bridge_reconfigure vswitchd/bridge.c:952:9
>> 8 0x9102a in bridge_run vswitchd/bridge.c:3439:9
>> 9 0xc8976 in main vswitchd/ovs-vswitchd.c:137:9
>> 10 0x2a1c9 in __libc_start_call_main
>> 11 0x2a28a in __libc_start_main
>> 12 0xb3ff4 in _start (vswitchd/ovs-vswitchd+0x734ff4)
>>
>> Reported by Clang 18 with UBsan on Ubuntu 24.04.
>>
>> Fixes: c8c49a9db9f2 ("netdev-linux: Properly access 32-bit aligned
>> rtnl_link_stats64 structs.")
>> Signed-off-by: Ilya Maximets <[email protected]>
>
> Reviewed-by: Simon Horman <[email protected]>
>
Regards,
Dumitru
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