Re: [PATCH 10/12] sata: sx4: fix pdc20621_get_from_dimm() on 64-bit

Damien Le Moal
2024-03-27T01:36:32Z

On 3/26/24 23:53, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> gcc warns about a memcpy() with overlapping pointers because of an
> incorrect size calculation:
>
> In file included from include/linux/string.h:369,
> from drivers/ata/sata_sx4.c:66:
> In function 'memcpy_fromio',
> inlined from 'pdc20621_get_from_dimm.constprop' at drivers/ata/sata_sx4.c:962:2:
> include/linux/fortify-string.h:97:33: error: '__builtin_memcpy' accessing 4294934464 bytes at offsets 0 and [16, 16400] overlaps 6442385281 bytes at offset -2147450817 [-Werror=restrict]
> 97 | #define __underlying_memcpy __builtin_memcpy
> | ^
> include/linux/fortify-string.h:620:9: note: in expansion of macro '__underlying_memcpy'
> 620 | __underlying_##op(p, q, __fortify_size); \
> | ^~~~~~~~~~~~~
> include/linux/fortify-string.h:665:26: note: in expansion of macro '__fortify_memcpy_chk'
> 665 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \
> | ^~~~~~~~~~~~~~~~~~~~
> include/asm-generic/io.h:1184:9: note: in expansion of macro 'memcpy'
> 1184 | memcpy(buffer, __io_virt(addr), size);
> | ^~~~~~
>
> The problem here is the overflow of an unsigned 32-bit number to a
> negative that gets converted into a signed 'long', keeping a large
> positive number.
>
> Replace the complex calculation with a more readable min() variant
> that avoids the warning.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

That is old :)

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Looks good to me. I can take the patch through libata tree, unless you prefer
taking the whole series ?

In case it is the latter:

Acked-by: Damien Le Moal <dlemoal@kernel.org>

--
Damien Le Moal
Western Digital Research