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libctf: make ctf_dump not crash on OOM

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ctf_dump calls ctf_str_append extensively but never checks to see if it
returns NULL (on OOM).  If it ever does, we truncate the string we are
appending to and leak it!

Instead, create a variant of ctf_str_append that returns the *original
string* on OOM, and use it in ctf-dump.  It is far better to omit a tiny
piece of a dump on OOM than to omit a bigger piece, and it is also
better to do this in what is after all purely debugging code than it is
to uglify ctf-dump.c with huge numbers of checks for the out-of-memory
case.  Slightly truncated debugging output is better than no debugging
output at all and an out-of-memory message.

New in v4.

libctf/
	* ctf-impl.h (ctf_str_append_noerr): Declare.
	* ctf-util.c (ctf_str_append_noerr): Define in terms of
	ctf_str_append.
	* ctf-dump.c (str_append): New, call it.
	(ctf_dump_format_type): Use str_append, not ctf_str_append.
	(ctf_dump_label): Likewise.
	(ctf_dump_objts): Likewise.
	(ctf_dump_funcs): Likewise.
	(ctf_dump_var): Likewise.
	(ctf_dump_member): Likewise.
	(ctf_dump_type): Likewise.
	(ctf_dump): Likewise.
This commit is contained in:
Nick Alcock 2019-09-17 06:57:00 +01:00
parent de07e349be
commit 9323dd869d
4 changed files with 61 additions and 23 deletions
Download patch file Download diff file Expand all files Collapse all files

15
libctf/ctf-util.c
View file

@ -103,7 +103,7 @@ ctf_sym_to_elf64 (const Elf32_Sym *src, Elf64_Sym *dst)
return dst;
}
/* A string appender working on dynamic strings. */
/* A string appender working on dynamic strings. Returns NULL on OOM. */
char *
ctf_str_append (char *s, const char *append)
@ -127,6 +127,19 @@ ctf_str_append (char *s, const char *append)
return s;
}
/* A version of ctf_str_append that returns the old string on OOM. */
char *
ctf_str_append_noerr (char *s, const char *append)
{
char *new_s;
new_s = ctf_str_append (s, append);
if (!new_s)
return s;
return new_s;
}
/* A realloc() that fails noisily if called with any ctf_str_num_users. */
void *
ctf_realloc (ctf_file_t *fp, void *ptr, size_t size)