From: Mark Wielaard <mark@klomp.org>
Date: Sat, 4 Dec 2021 00:08:48 +0000 (+0100)
Subject: readelf: Workaround stringop-truncation error
X-Git-Tag: elfutils-0.187~75
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3e1e249bfd8455457716cce798f3f91d01f2f00d;p=thirdparty%2Felfutils.git

readelf: Workaround stringop-truncation error

In function ‘strncpy’,
    inlined from ‘print_ehdr’ at readelf.c:1175:4:
error: ‘__builtin_strncpy’ specified bound 512 equals destination size
       [-Werror=stringop-truncation]

strncpy doesn't terminate the copied string if there is not enough
room. We compensate later by explicitly adding a zero terminator at
buf[sizeof (buf) - 1]. Normally gcc does see this, but with
-fsanitize=address there is too much (checking) code in between. But
it is actually better to not let strncpy do too much work, so
substract one from the size.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---

diff --git a/src/ChangeLog b/src/ChangeLog
index 05b2522d3..263e9faaf 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2021-12-04  Mark Wielaard  <mark@klomp.org>
+
+	* readelf.c (print_ehdr): Pass sizeof (buf) - 1 to strncpy.
+
 2021-10-20  John M Mellor-Crummey  <johnmc@rice.edu>
 
 	* readelf.c (print_debug_line_section): Try to read
diff --git a/src/readelf.c b/src/readelf.c
index c10038e34..93fb5989e 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -1172,7 +1172,7 @@ print_ehdr (Ebl *ebl, GElf_Ehdr *ehdr)
 		  (uint32_t) shdr->sh_link);
       else
 	{
-	  strncpy (buf, _(" ([0] not available)"), sizeof (buf));
+	  strncpy (buf, _(" ([0] not available)"), sizeof (buf) - 1);
 	  buf[sizeof (buf) - 1] = '\0';
 	}