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libctf, serialize: functions with no args have a NULL dtd_vlen

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Every place that accesses a function's dtd_vlen accesses it only if the
number of args is nonzero, except the serializer, which always tries to
memcpy it.  The number of bytes it memcpys in this case is zero, but it
is still undefined behaviour to copy zero bytes from a null pointer.
So check for this case explicitly.

libctf/ChangeLog
2021-03-25  Nick Alcock  <nick.alcock@oracle.com>

	PR libctf/27628
	* ctf-serialize.c (ctf_emit_type_sect): Allow for a NULL vlen in
	CTF_K_FUNCTION types.
This commit is contained in:
Nick Alcock 2021-03-25 16:32:46 +00:00
parent 24c877f9b1
commit 86f64bf43f
2 changed files with 9 additions and 1 deletions
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6
libctf/ChangeLog
View File

@ -1,3 +1,9 @@
2021-03-25 Nick Alcock <nick.alcock@oracle.com>
PR libctf/27628
* ctf-serialize.c (ctf_emit_type_sect): Allow for a NULL vlen in
CTF_K_FUNCTION types.
2021-03-25 Nick Alcock <nick.alcock@oracle.com>
* ctf-dump.c (ctf_dump_format_type): Don't emit size or alignment

4
libctf/ctf-serialize.c
View File

@ -849,7 +849,9 @@ ctf_emit_type_sect (ctf_dict_t *fp, unsigned char **tptr)
break;
case CTF_K_FUNCTION:
memcpy (t, dtd->dtd_vlen, sizeof (uint32_t) * (vlen + (vlen & 1)));
/* Functions with no args also have no vlen. */
if (dtd->dtd_vlen)
memcpy (t, dtd->dtd_vlen, sizeof (uint32_t) * (vlen + (vlen & 1)));
t += sizeof (uint32_t) * (vlen + (vlen & 1));
break;