libctf, ld: diagnose corrupted CTF header cth_strlen

The last section in a CTF dict is the string table, at an offset
represented by the cth_stroff header field.  Its length is recorded in
the next field, cth_strlen, and the two added together are taken as the
size of the CTF dict.  Upon opening a dict, we check that none of the
header offsets exceed this size, and we check when uncompressing a
compressed dict that the result of the uncompression is the same length:
but CTF dicts need not be compressed, and short ones are not.
Uncompressed dicts just use the ctf_size without checking it.  This
field is thankfully almost unused: it is mostly used when reserializing
a dict, which can't be done to dicts read off disk since they're
read-only.

However, when opening an uncompressed foreign-endian dict we have to
copy it out of the mmaped region it is stored in so we can endian-
swap it, and we use ctf_size when doing that.  When the cth_strlen is
corrupt, this can overrun.

Fix this by checking the ctf_size in all uncompressed cases, just as we
already do in the compressed case.  Add a new test.

This came to light because various corrupted-CTF raw-asm tests had an
incorrect cth_strlen: fix all of them so they produce the expected
error again.

libctf/
	PR libctf/28933
	* ctf-open.c (ctf_bufopen_internal): Always check uncompressed
	CTF dict sizes against the section size in case the cth_strlen is
	corrupt.

ld/
	PR libctf/28933
	* testsuite/ld-ctf/diag-strlen-invalid.*: New test,
	derived from diag-cttname-invalid.s.
	* testsuite/ld-ctf/diag-cttname-invalid.s: Fix incorrect cth_strlen.
	* testsuite/ld-ctf/diag-cttname-null.s: Likewise.
	* testsuite/ld-ctf/diag-cuname.s: Likewise.
	* testsuite/ld-ctf/diag-parlabel.s: Likewise.
	* testsuite/ld-ctf/diag-parname.s: Likewise.

ld/testsuite/ld-ctf/diag-cttname-invalid.s

@@ -15,7 +15,7 @@
 	.long	0x8
 	.long	0x10
 	.long	0x40
-	.long	0x42
+	.long	0x37
 	.long	0x1
 	.long	0x7
 	.long	0x7

ld/testsuite/ld-ctf/diag-cttname-null.s

@@ -15,7 +15,7 @@
 	.long	0x8
 	.long	0x10
 	.long	0x40
-	.long	0x42
+	.long	0x37
 	.long	0x1
 	.long	0x7
 	.long	0x7

ld/testsuite/ld-ctf/diag-cuname.s

@@ -15,7 +15,7 @@
 	.long	0x8
 	.long	0x10
 	.long	0x40
-	.long	0x42
+	.long	0x37
 	.long	0x1
 	.long	0x7
 	.long	0x7

ld/testsuite/ld-ctf/diag-parlabel.s

@@ -15,7 +15,7 @@
 	.long	0x8
 	.long	0x10
 	.long	0x40
-	.long	0x42
+	.long	0x37
 	.long	0x1
 	.long	0x7
 	.long	0x7

ld/testsuite/ld-ctf/diag-parname.s

@@ -15,7 +15,7 @@
 	.long	0x8
 	.long	0x10
 	.long	0x40
-	.long	0x42
+	.long	0x37
 	.long	0x1
 	.long	0x7
 	.long	0x7

ld/testsuite/ld-ctf/diag-strlen-invalid.d

@@ -0,0 +1,5 @@
+#as:
+#source: diag-strlen-invalid.s
+#ld: -shared
+#name: Diagnostics - String offset invalid.
+#warning: .* byte long CTF dictionary overruns .* byte long CTF section

ld/testsuite/ld-ctf/diag-strlen-invalid.s

@@ -0,0 +1,44 @@
+	.file	"A.c"
+	.section	.ctf,"",@progbits
+.Lctf0:
+	.2byte	0xdff2
+	.byte	0x4
+	.byte	0
+	.long	0
+	.long	0
+	.long	0x9
+	.long	0
+	.long	0
+	.long	0x4
+	.long	0x4
+	.long	0x8
+	.long	0x8
+	.long	0x10
+	.long	0x40
+	.long	0x42
+	.long	0x1
+	.long	0x7
+	.long	0x7
+	.long	0x1
+	.long	0xff00
+	.long	0x1a000001
+	.long	0x8
+	.long	0x5
+	.long	0
+	.long	0x3
+	.long	0x3
+	.long	0x26000000
+	.long	0x6
+	.long	0
+	.long	0xe000000
+	.long	0x2
+	.ascii "\0"
+	.ascii "A\0"
+	.ascii "B\0"
+	.ascii "b\0"
+	.ascii "a\0"
+	.ascii "/usr/src/binutils-gdb/ld/testsuite/ld-ctf/A.c\0"
+	.text
+	.comm	a,8,8
+	.ident	"GCC: (GNU) 8.3.1 20191121 (Red Hat 8.3.1-5.0.1)"
+	.section	.note.GNU-stack,"",@progbits

libctf/ctf-open.c

@@ -1517,7 +1517,19 @@ ctf_bufopen_internal (const ctf_sect_t *ctfsect, const ctf_sect_t *symsect,
 	  goto bad;
 	}
     }
-  else if (foreign_endian)
+  else
+    {
+      if (_libctf_unlikely_ (ctfsect->cts_size < hdrsz + fp->ctf_size))
+	{
+	  ctf_err_warn (NULL, 0, ECTF_CORRUPT,
+			_("%lu byte long CTF dictionary overruns %lu byte long CTF section"),
+			(unsigned long) ctfsect->cts_size,
+			(unsigned long) (hdrsz + fp->ctf_size));
+	  err = ECTF_CORRUPT;
+	  goto bad;
+	}
+
+      if (foreign_endian)
 	{
 	  if ((fp->ctf_base = malloc (fp->ctf_size)) == NULL)
 	    {
@@ -1531,13 +1543,14 @@ ctf_bufopen_internal (const ctf_sect_t *ctfsect, const ctf_sect_t *symsect,
 	}
       else
 	{
-      /* We are just using the section passed in -- but its header may be an old
-	 version.  Point ctf_buf past the old header, and never touch it
-	 again.  */
+	  /* We are just using the section passed in -- but its header may
+	     be an old version.  Point ctf_buf past the old header, and
+	     never touch it again.  */
 	  fp->ctf_base = (unsigned char *) ctfsect->cts_data;
 	  fp->ctf_dynbase = NULL;
 	  fp->ctf_buf = fp->ctf_base + hdrsz;
 	}
+    }
 
   /* Once we have uncompressed and validated the CTF data buffer, we can
      proceed with initializing the ctf_dict_t we allocated above.