linux-kernel - [PATCH] firmware: tegra: bpmp: refactor deprecated strncpy

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Message-ID: <20230913-strncpy-drivers-firmware-tegra-bpmp-debugfs-c-v1-1-828b0a8914b5@google.com>
Date:   Wed, 13 Sep 2023 19:38:44 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] firmware: tegra: bpmp: refactor deprecated strncpy

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

We should prefer more robust and less ambiguous string interfaces.

It seems like the filename stored at `namevirt` is expected to be
NUL-terminated.

A suitable replacement is `strscpy_pad` due to the fact that it
guarantees NUL-termination on the destination buffer whilst maintaining
the NUL-padding behavior that strncpy provides.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: compile tested only.
---
 drivers/firmware/tegra/bpmp-debugfs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/tegra/bpmp-debugfs.c b/drivers/firmware/tegra/bpmp-debugfs.c
index 6dfe3d34109e..bbcdd9fed3fb 100644
--- a/drivers/firmware/tegra/bpmp-debugfs.c
+++ b/drivers/firmware/tegra/bpmp-debugfs.c
@@ -610,7 +610,7 @@ static int debugfs_show(struct seq_file *m, void *p)
 	}
 
 	len = strlen(filename);
-	strncpy(namevirt, filename, namesize);
+	strscpy_pad(namevirt, filename, namesize);
 
 	err = mrq_debugfs_read(bpmp, namephys, len, dataphys, datasize,
 			       &nbytes);
@@ -661,7 +661,7 @@ static ssize_t debugfs_store(struct file *file, const char __user *buf,
 	}
 
 	len = strlen(filename);
-	strncpy(namevirt, filename, namesize);
+	strscpy_pad(namevirt, filename, namesize);
 
 	if (copy_from_user(datavirt, buf, count)) {
 		err = -EFAULT;

---
base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
change-id: 20230913-strncpy-drivers-firmware-tegra-bpmp-debugfs-c-54f7baaf32c0

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