[PATCH] arm: mach-snapdragon: warn on root compatible string truncation

[Vivek Ray]

The configure_env() function copies root compatible strings into a
32-byte buffer prior to parsing. If a compatible string exceeds this
limit, strlcpy() silently truncates it, producing a malformed fdtfile
path and a boot failure with no indication of the root cause.

Add explicit truncation checks after both strlcpy() calls and emit a
log_warning() with the offending compatible string to make such
failures easier to diagnose.

Signed-off-by: Vivek Ray <vk092kumar at gmail.com>
---
 arch/arm/mach-snapdragon/board.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-snapdragon/board.c b/arch/arm/mach-snapdragon/board.c
index 829a0109ac7..9324030ae4d 100644
--- a/arch/arm/mach-snapdragon/board.c
+++ b/arch/arm/mach-snapdragon/board.c
@@ -391,6 +391,7 @@ static void configure_env(void)
 	const char *first_compat, *last_compat;
 	char *tmp;
 	char buf[32] = { 0 };
+	int len = 0;
 	/*
 	 * Most DTB filenames follow the scheme: qcom/<soc>-[vendor]-<board>.dtb
 	 * The vendor is skipped when it's a Qualcomm reference board, or the
@@ -417,7 +418,10 @@ static void configure_env(void)
 		return;
 	}
 
-	strlcpy(buf, first_compat, sizeof(buf) - 1);
+	/* A safety check to avoid silent failure due to name truncation */
+	len = strlcpy(buf, first_compat, sizeof(buf) - 1);
+	if (len >= sizeof(buf) - 1)
+		log_warning("compatible '%s' got truncated, fdtfile name too long\n", first_compat);
 	tmp = buf;
 
 	/* The Qualcomm reference boards (RBx, HDK, etc)  */
@@ -468,7 +472,11 @@ static void configure_env(void)
 
 		/* Copy the last compat (e.g. "qcom,sdm845") into buf */
 		memset(buf, 0, sizeof(buf));
-		strlcpy(buf, last_compat, sizeof(buf) - 1);
+
+		/* check for name truncation */
+		len = strlcpy(buf, last_compat, sizeof(buf) - 1);
+		if (len >= sizeof(buf) - 1)
+			log_warning("compatible '%s' got truncated, fdtfile name too long\n", last_compat);
 		tmp = buf;
 
 		/* strsep() is destructive, it replaces the comma with a \0 */
-- 
2.34.1