[PATCH 5/5] commands: fix unaligned accesses of aliased commands on amd64

[Ahmad Fatoum <ahmad@a3f.at>]

If a command has aliases (e.g. edit and sedit), register_command
allocates a new struct command for the alias. As struct command has a
alignment of 64 specified on __x86_64__, this new allocation needs to
observe the alignment lest unaligned access could occur. I don't think
it's likely that GCC would generate SIMD code here that expects a 64 byte
alignment, but heed UBSan's advice and use xmemalign with the appropriate
alignment.

Fixes: 8c14b97758 ("svn_rev_477")
Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
---
I am not sure about this, because I don't understand why there was a 64
bit alignment in the x86_64 linker script in the first place.
The fix is trivial though, so even if it's only a theoretical, lets have
it? 
---
 common/command.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/common/command.c b/common/command.c
index d9cc4a6d4887..09655e9e78d5 100644
--- a/common/command.c
+++ b/common/command.c
@@ -106,7 +106,7 @@ int register_command(struct command *cmd)
 	if (cmd->aliases) {
 		const char * const *aliases = cmd->aliases;
 		while(*aliases) {
-			struct command *c = xzalloc(sizeof(struct command));
+			struct command *c = xmemalign(__alignof__(*c), sizeof *c);
 
 			memcpy(c, cmd, sizeof(struct command));
 
-- 
2.20.1


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