[1/3] libxcmd: don't crash if el_gets returns null

Commit Message

Darrick J. Wong May 9, 2020, 4:29 p.m. UTC

From: Darrick J. Wong <[e-mail]>

el_gets returns NULL if it fails to read any characters (due to EOF or
errors occurred).  strdup will crash if it is fed a NULL string, so
check the return value to avoid segfaulting.

Signed-off-by: Darrick J. Wong <[e-mail]>
---
 libxcmd/input.c |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

Comments

Christoph Hellwig May 9, 2020, 4:36 p.m. UTC | #1

On Sat, May 09, 2020 at 09:29:37AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <[e-mail]>
> 
> el_gets returns NULL if it fails to read any characters (due to EOF or
> errors occurred).  strdup will crash if it is fed a NULL string, so
> check the return value to avoid segfaulting.

Didn't I review this already?

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/libxcmd/input.c b/libxcmd/input.c
index 137856e3..a4548d7c 100644
--- a/libxcmd/input.c
+++ b/libxcmd/input.c
@@ -47,6 +47,7 @@  fetchline(void)
 	static EditLine	*el;
 	static History	*hist;
 	HistEvent	hevent;
+	const char	*cmd;
 	char		*line;
 	int		count;
 
@@ -59,13 +60,18 @@  fetchline(void)
 		el_set(el, EL_PROMPT, el_get_prompt);
 		el_set(el, EL_HIST, history, (const char *)hist);
 	}
-	line = strdup(el_gets(el, &count));
-	if (line) {
-		if (count > 0)
-			line[count-1] = '\0';
-		if (*line)
-			history(hist, &hevent, H_ENTER, line);
-	}
+	cmd = el_gets(el, &count);
+	if (!cmd)
+		return NULL;
+
+	line = strdup(cmd);
+	if (!line)
+		return NULL;
+
+	if (count > 0)
+		line[count-1] = '\0';
+	if (*line)
+		history(hist, &hevent, H_ENTER, line);
 	return line;
 }
 #else