arm64/sysreg: Fix broken strncpy() -> strscpy() conversion

Mostafa reports that commit d232606773a0 ("arm64/sysreg: refactor
deprecated strncpy") breaks our early command-line parsing because the
original code is working on space-delimited substrings rather than
NUL-terminated strings.

Rather than simply reverting the broken conversion patch, replace the
strscpy() with a simple memcpy() with an explicit NUL-termination of the
result.

Reported-by: Mostafa Saleh <[email protected]>
Tested-by: Mostafa Saleh <[email protected]>
Fixes: d232606773a0 ("arm64/sysreg: refactor deprecated strncpy")
Signed-off-by: Justin Stitt <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index aee12c75b738..3addc09f8746 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -262,9 +262,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 		if (!len)
 			return;
 
-		len = strscpy(buf, cmdline, ARRAY_SIZE(buf));
-		if (len == -E2BIG)
-			len = ARRAY_SIZE(buf) - 1;
+		len = min(len, ARRAY_SIZE(buf) - 1);
+		memcpy(buf, cmdline, len);
+		buf[len] = '\0';
 
 		if (strcmp(buf, "--") == 0)
 			return;