[PATCH v2] arm: mach-snapdragon: increase compat buffer size and 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 silent boot failure with no indication of the root cause.

Bump buf[] to 128 bytes and dt_path[] to 256 bytes to accommodate longer
compatible strings. Also, 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>

---

Changes in V2:
- Bump buf[] from 32 to 128 bytes and dt_path[] from 64 to 256 (Casey Connolly)
- Fix line size check, use > not >= (Casey Connolly)

---
 arch/arm/mach-snapdragon/board.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mach-snapdragon/board.c b/arch/arm/mach-snapdragon/board.c
index 829a0109ac7..d9390d9b5d3 100644
--- a/arch/arm/mach-snapdragon/board.c
+++ b/arch/arm/mach-snapdragon/board.c
@@ -390,13 +390,14 @@ static void configure_env(void)
 {
 	const char *first_compat, *last_compat;
 	char *tmp;
-	char buf[32] = { 0 };
+	char buf[128] = { 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
 	 * db845c.
 	 */
-	char dt_path[64] = { 0 };
+	char dt_path[256] = { 0 };
 	int compat_count, ret;
 	ofnode root;
 
@@ -417,7 +418,11 @@ 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 +473,12 @@ 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