qed: replace uses of strncpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

This patch eliminates three uses of strncpy():

Firstly, `dest` is expected to be NUL-terminated which is evident by the
manual setting of a NUL-byte at size - 1. For this use specifically,
strscpy() is a viable replacement due to the fact that it guarantees
NUL-termination on the destination buffer.

The next two cases should simply be memcpy() as the size of the src
string is always 3 and the destination string just wants the first 3
bytes changed.

To be clear, there are no buffer overread bugs in the current code as
the sizes and offsets are carefully managed such that buffers are
NUL-terminated. However, with these changes, the code is now more robust
and less ambiguous (and hopefully easier to read).

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231012-strncpy-drivers-net-ethernet-qlogic-qed-qed_debug-c-v2-1-16d2c0162b80@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/net/ethernet/qlogic/qed/qed_debug.c b/drivers/net/ethernet/qlogic/qed/qed_debug.c
index cdcead614e9f..f67be4b8ad43 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_debug.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_debug.c
@@ -3204,8 +3204,8 @@ static u32 qed_grc_dump_big_ram(struct qed_hwfn *p_hwfn,
 		     BIT(big_ram->is_256b_bit_offset[dev_data->chip_id]) ? 256
 									 : 128;
 
-	strncpy(type_name, big_ram->instance_name, BIG_RAM_NAME_LEN);
-	strncpy(mem_name, big_ram->instance_name, BIG_RAM_NAME_LEN);
+	memcpy(type_name, big_ram->instance_name, BIG_RAM_NAME_LEN);
+	memcpy(mem_name, big_ram->instance_name, BIG_RAM_NAME_LEN);
 
 	/* Dump memory header */
 	offset += qed_grc_dump_mem_hdr(p_hwfn,
@@ -6359,8 +6359,7 @@ static void qed_read_str_from_buf(void *buf, u32 *offset, u32 size, char *dest)
 {
 	const char *source_str = &((const char *)buf)[*offset];
 
-	strncpy(dest, source_str, size);
-	dest[size - 1] = '\0';
+	strscpy(dest, source_str, size);
 	*offset += size;
 }