From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Mon, 2 Feb 2026 18:28:32 +0000 (+0100)
Subject: dmesg: Only check for newline if input exists
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4f6b555f6c1aa7eb529b162385e92e0bb9bebcb7;p=thirdparty%2Futil-linux.git

dmesg: Only check for newline if input exists

If a memory mapped file does not end with a newline, do not check for
its existence. Accessing *end would lead to an out of boundary read.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
---

diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index 12e40a350..3259f3d64 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -946,15 +946,15 @@ static int get_next_syslog_record(struct dmesg_control *ctl,
 			rec->mesg_size = end - begin;
 		}
 
-		/* Don't count \n from the last message to the message size */
-		if (*end != '\n' && *(end - 1) == '\n')
-			rec->mesg_size--;
-
 		rec->next_size -= end - rec->next;
 		rec->next = rec->next_size > 0 ? end + 1 : NULL;
 		if (rec->next_size > 0)
 			rec->next_size--;
 
+		/* Don't count \n from the last message to the message size */
+		if ((!rec->next || *end != '\n') && *(end - 1) == '\n')
+			rec->mesg_size--;
+
 		return 0;
 	}