[PATCH] ARM: atags_compat: avoid -Warray-bounds warning

From: Arnd Bergmann
Date: Mon Oct 26 2020 - 18:14:13 EST


From: Arnd Bergmann <arnd@xxxxxxxx>

gcc-11 reports a struct member overflow when copying a string
into a single-character array:

In file included from arch/arm/kernel/atags_compat.c:17:
In function 'strcpy',
inlined from 'build_tag_list' at arch/arm/kernel/atags_compat.c:200:2:
include/linux/string.h:287:29: warning: '__builtin_strcpy' offset 108 from the object at 'taglist' is out of the bounds of referenced subobject 'cmdline' with type 'char[1]' at offset 108 [-Warray-bounds]
287 | #define __underlying_strcpy __builtin_strcpy
| ^
include/linux/string.h:481:10: note: in expansion of macro '__underlying_strcpy'
481 | return __underlying_strcpy(p, q);
| ^~~~~~~~~~~~~~~~~~~
In file included from arch/arm/include/asm/setup.h:14,
from arch/arm/kernel/atags_compat.c:20:
arch/arm/kernel/atags_compat.c: In function 'build_tag_list':
arch/arm/include/uapi/asm/setup.h:127:7: note: subobject 'cmdline' declared here
127 | char cmdline[1]; /* this is the minimum size */
| ^~~~~~~

The code is otherwise correct, so just shut up the warning by
not letting the compiler see the underlying type.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
arch/arm/kernel/atags_compat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/kernel/atags_compat.c b/arch/arm/kernel/atags_compat.c
index 10da11c212cc..3f1f631763ba 100644
--- a/arch/arm/kernel/atags_compat.c
+++ b/arch/arm/kernel/atags_compat.c
@@ -197,7 +197,7 @@ static void __init build_tag_list(struct param_struct *params, void *taglist)
tag->hdr.tag = ATAG_CMDLINE;
tag->hdr.size = (strlen(params->commandline) + 3 +
sizeof(struct tag_header)) >> 2;
- strcpy(tag->u.cmdline.cmdline, params->commandline);
+ strcpy((void*)&tag->u, params->commandline);

tag = tag_next(tag);
tag->hdr.tag = ATAG_NONE;
--
2.27.0