File s390-tools-sles15sp2-04-zipl-libc-Indicate-trun... of Package s390-tools.15932

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File s390-tools-sles15sp2-04-zipl-libc-Indicate-truncated-lines-in-printf-with.patch of Package s390-tools.15932

Subject: [PATCH] [BZ 184060] zipl/libc: Indicate truncated lines in printf with '...'
From: Philipp Rudo <prudo@linux.ibm.com>

Description:   zipl/libc: Fix potential buffer overflow in printf
Symptom:       Crash of the zipl boot loader during boot.
Problem:       The zipl boot loaders have their own minimalistic libc
               implementation. In it printf and sprintf use vsprintf for string
               formatting. Per definition vsprintf assumes that the buffer it
               writes to is large enough to contain the formatted string and
               performs no size checks. This is problematic for the boot
               loaders because the buffer they use are often allocated on the
               stack. Thus even small changes to the string format can
               potentially cause buffer overflows on the stack.
Solution:      Implement vsnprintf and make use of it.
Reproduction:  Use printf to print a string with >81 characters (exact number
               depends on the stack layout/compiler used).
Upstream-ID:   36fed0e6c6590631c4ce1707c8fe3c3397bcce4d
Problem-ID:    184060

Upstream-Description:

zipl/libc: Indicate truncated lines in printf with '...'

Append '...' to lines exceeding the maximum line length instead of
              silently truncating them.

Suggested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
              Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
              Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
              Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
              Signed-off-by: Jan Hoeppner <hoeppner@linux.ibm.com>

Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
---
 zipl/boot/libc.c |   10 ++++++++--
 zipl/boot/libc.h |    1 +
 zipl/boot/menu.h |    1 -
 3 files changed, 9 insertions(+), 3 deletions(-)

--- a/zipl/boot/libc.c
+++ b/zipl/boot/libc.c
@@ -408,11 +408,17 @@ void snprintf(char *buf, unsigned long s
  */
 void printf(const char *fmt, ...)
 {
-	char buf[81];
+	char buf[LINE_LENGTH + 1];
+	int len;
 	va_list va;
 
 	va_start(va, fmt);
-	vsnprintf(buf, sizeof(buf), fmt, va);
+	len = vsnprintf(buf, sizeof(buf), fmt, va);
+	if (len > LINE_LENGTH) {
+		buf[LINE_LENGTH - 1] = '.';
+		buf[LINE_LENGTH - 2] = '.';
+		buf[LINE_LENGTH - 3] = '.';
+	}
 	sclp_print(buf);
 	va_end(va);
 }
--- a/zipl/boot/libc.h
+++ b/zipl/boot/libc.h
@@ -40,6 +40,7 @@
 #define ENOTTY		25	/* Not a typewriter */
 
 #define MIB	(1024ULL * 1024)
+#define LINE_LENGTH 80 /* max line length printed by printf */
 
 typedef unsigned long long uint64_t;
 typedef unsigned int uint32_t;
--- a/zipl/boot/menu.h
+++ b/zipl/boot/menu.h
@@ -20,7 +20,6 @@
 /* max command line length */
 #define COMMAND_LINE_SIZE	        896
 #define BOOT_MENU_ENTRIES		63
-#define LINE_LENGTH                     80
 #define PARAM_SIZE                      8
 #define TEXT_OFFSET                     4

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