[PATCH] trace: events: cleanup deprecated strncpy uses

[Justin Stitt <justinstitt@google.com>]

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

For 2 out of 3 of these changes we can simply swap in strscpy() as it
guarantess NUL-termination which is needed for the following trace
print.

trace_rpcgss_context() should use memcpy as its format specifier %.*s
allows for the length to be specifier (__entry->len). Due to this,
acceptor does not technically need to be NUL-terminated. Moreover,
swapping in strscpy() and keeping everything else the same could result
in truncation of the source string by one byte. To remedy this, we could
use `len + 1` but I am unsure of the size of the destination buffer so a
simple memcpy should suffice.
|	TP_printk("win_size=%u expiry=%lu now=%lu timeout=%u acceptor=%.*s",
|		__entry->window_size, __entry->expiry, __entry->now,
|		__entry->timeout, __entry->len, __get_str(acceptor))

I suspect acceptor not to naturally be a NUL-terminated string due to
the presence of some stringify methods.
|	.crstringify_acceptor	= gss_stringify_acceptor,

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
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 include/trace/events/mdio.h   | 2 +-
 include/trace/events/rpcgss.h | 2 +-
 include/trace/events/sock.h   | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/trace/events/mdio.h b/include/trace/events/mdio.h
index 0f241cbe00ab..285b3e4f83ba 100644
--- a/include/trace/events/mdio.h
+++ b/include/trace/events/mdio.h
@@ -25,7 +25,7 @@ TRACE_EVENT_CONDITION(mdio_access,
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->busid, bus->id, MII_BUS_ID_SIZE);
+		strscpy(__entry->busid, bus->id, MII_BUS_ID_SIZE);
 		__entry->read = read;
 		__entry->addr = addr;
 		__entry->regnum = regnum;
diff --git a/include/trace/events/rpcgss.h b/include/trace/events/rpcgss.h
index ba2d96a1bc2f..274c297f1b15 100644
--- a/include/trace/events/rpcgss.h
+++ b/include/trace/events/rpcgss.h
@@ -618,7 +618,7 @@ TRACE_EVENT(rpcgss_context,
 		__entry->timeout = timeout;
 		__entry->window_size = window_size;
 		__entry->len = len;
-		strncpy(__get_str(acceptor), data, len);
+		memcpy(__get_str(acceptor), data, len);
 	),
 
 	TP_printk("win_size=%u expiry=%lu now=%lu timeout=%u acceptor=%.*s",
diff --git a/include/trace/events/sock.h b/include/trace/events/sock.h
index fd206a6ab5b8..1d0b98e6b2cc 100644
--- a/include/trace/events/sock.h
+++ b/include/trace/events/sock.h
@@ -109,7 +109,7 @@ TRACE_EVENT(sock_exceed_buf_limit,
 	),
 
 	TP_fast_assign(
-		strncpy(__entry->name, prot->name, 32);
+		strscpy(__entry->name, prot->name, 32);
 		__entry->sysctl_mem[0] = READ_ONCE(prot->sysctl_mem[0]);
 		__entry->sysctl_mem[1] = READ_ONCE(prot->sysctl_mem[1]);
 		__entry->sysctl_mem[2] = READ_ONCE(prot->sysctl_mem[2]);

---
base-commit: 928a87efa42302a23bb9554be081a28058495f22
change-id: 20240401-strncpy-include-trace-events-mdio-h-0a325676b468

Best regards,
--
Justin Stitt <justinstitt@google.com>