[PATCH v1 1/1] readelf: invalid error message triggered when last tag is an empty string

[Matthieu Longo]

Disclaimer: this issue cannot occur with Object Attributes v1 (OAv1) because
a value of '\0' (empty string) for a tag with a string value is considered
as the default value for the attribute, and consequently is eliminated
from the output object during the serialization.

In the context of OAv2 [1], an empty string is a valid value for a string
attribute tag, and can be saved as a tag might not have a default value.
In the case where this tag is last in the object attributes section, the
current check incorrectly detects an overflow, and prints out an error
message for a corrupted string tag.

This patch fixes the detection of the overflow so that it now accept an
empty string in the last tag of the object attributes section.

Today, no test can be added since the bug cannot be triggered in the context
of OAv1. This fix was tested in the context of OAv2's patch series [1] that
will add tests to cover this specific use case.

[1]: https://inbox.sourceware.org/binutils/20250509151319.88725-1-matthieu
     .longo@arm.com/
---
 binutils/readelf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/binutils/readelf.c b/binutils/readelf.c
index dd1871d8c75..88edf9246cc 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -17779,12 +17779,14 @@ display_tag_value (signed int tag,
   else if (tag & 1)
     {
       /* PR 17531 file: 027-19978-0.004.  */
-      size_t maxlen = (end - p) - 1;
+      size_t maxlen = end - p;
 
       putchar ('"');
       if (maxlen > 0)
 	{
-	  print_symbol_name ((int) maxlen, (const char *) p);
+	  maxlen -= 1; /* Remove \0 from the character count.  */
+	  if (maxlen > 0) /* Don't try to print an empty string.  */
+	    print_symbol_name ((int) maxlen, (const char *) p);
 	  p += strnlen ((char *) p, maxlen) + 1;
 	}
       else
-- 
2.50.0