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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
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15
libctf/ChangeLog
View File

@ -1,3 +1,18 @@
2019-09-23 Nick Alcock <nick.alcock@oracle.com>
* 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.
2019-09-23 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_alloc): Remove.

53
libctf/ctf-dump.c
View File

@ -20,6 +20,8 @@
#include <ctf-impl.h>
#include <string.h>
#define str_append(s, a) ctf_str_append_noerr (s, a)
/* One item to be dumped, in string form. */
typedef struct ctf_dump_item
@ -119,7 +121,7 @@ ctf_dump_format_type (ctf_file_t *fp, ctf_id_t id, int flag)
{
if (id == 0 || ctf_errno (fp) == ECTF_NONREPRESENTABLE)
{
str = ctf_str_append (str, " (type not represented in CTF)");
str = str_append (str, " (type not represented in CTF)");
ctf_set_errno (fp, ECTF_NOTREF);
break;
}
@ -147,13 +149,13 @@ ctf_dump_format_type (ctf_file_t *fp, ctf_id_t id, int flag)
}
free (buf);
buf = NULL;
str = ctf_str_append (str, bit);
str = str_append (str, bit);
free (bit);
bit = NULL;
new_id = ctf_type_reference (fp, id);
if (new_id != CTF_ERR)
str = ctf_str_append (str, " ->");
str = str_append (str, " ->");
} while (new_id != CTF_ERR);
if (ctf_errno (fp) != ECTF_NOTREF)
@ -319,7 +321,7 @@ ctf_dump_label (const char *name, const ctf_lblinfo_t *info,
return -1; /* errno is set for us. */
}
str = ctf_str_append (str, typestr);
str = str_append (str, typestr);
free (typestr);
ctf_dump_append (state, str);
@ -376,7 +378,7 @@ ctf_dump_objts (ctf_file_t *fp, ctf_dump_state_t *state)
return -1; /* errno is set for us. */
}
str = ctf_str_append (str, typestr);
str = str_append (str, typestr);
free (typestr);
ctf_dump_append (state, str);
@ -426,7 +428,7 @@ ctf_dump_funcs (ctf_file_t *fp, ctf_dump_state_t *state)
goto err;
}
str = ctf_str_append (str, " ");
str = str_append (str, " ");
/* Function name. */
@ -441,8 +443,8 @@ ctf_dump_funcs (ctf_file_t *fp, ctf_dump_state_t *state)
if (asprintf (&bit, "%s (0x%lx) ", sym_name, (unsigned long) i) < 0)
goto oom;
}
str = ctf_str_append (str, bit);
str = ctf_str_append (str, " (");
str = str_append (str, bit);
str = str_append (str, " (");
free (bit);
/* Function arguments. */
@ -460,15 +462,15 @@ ctf_dump_funcs (ctf_file_t *fp, ctf_dump_state_t *state)
err = "look up argument type name";
goto err;
}
str = ctf_str_append (str, bit);
str = str_append (str, bit);
if ((j < fi.ctc_argc - 1) || (fi.ctc_flags & CTF_FUNC_VARARG))
str = ctf_str_append (str, ", ");
str = str_append (str, ", ");
free (bit);
}
if (fi.ctc_flags & CTF_FUNC_VARARG)
str = ctf_str_append (str, "...");
str = ctf_str_append (str, ")");
str = str_append (str, "...");
str = str_append (str, ")");
free (args);
ctf_dump_append (state, str);
@ -507,7 +509,7 @@ ctf_dump_var (const char *name, ctf_id_t type, void *arg)
return -1; /* errno is set for us. */
}
str = ctf_str_append (str, typestr);
str = str_append (str, typestr);
free (typestr);
ctf_dump_append (state, str);
@ -526,7 +528,7 @@ ctf_dump_member (const char *name, ctf_id_t id, unsigned long offset,
ssize_t i;
for (i = 0; i < depth; i++)
*state->cdm_str = ctf_str_append (*state->cdm_str, " ");
*state->cdm_str = str_append (*state->cdm_str, " ");
if ((typestr = ctf_type_aname (state->cdm_fp, id)) == NULL)
{
@ -536,7 +538,7 @@ ctf_dump_member (const char *name, ctf_id_t id, unsigned long offset,
offset) < 0)
goto oom;
*state->cdm_str = ctf_str_append (*state->cdm_str, bit);
*state->cdm_str = str_append (*state->cdm_str, bit);
free (typestr);
free (bit);
return 0;
@ -549,7 +551,7 @@ ctf_dump_member (const char *name, ctf_id_t id, unsigned long offset,
offset, id, ctf_type_kind (state->cdm_fp, id), typestr, name,
(unsigned long) ctf_type_align (state->cdm_fp, id)) < 0)
goto oom;
*state->cdm_str = ctf_str_append (*state->cdm_str, bit);
*state->cdm_str = str_append (*state->cdm_str, bit);
free (typestr);
free (bit);
typestr = NULL;
@ -563,12 +565,12 @@ ctf_dump_member (const char *name, ctf_id_t id, unsigned long offset,
if (asprintf (&bit, ", format 0x%x, offset:bits 0x%x:0x%x", ep.cte_format,
ep.cte_offset, ep.cte_bits) < 0)
goto oom;
*state->cdm_str = ctf_str_append (*state->cdm_str, bit);
*state->cdm_str = str_append (*state->cdm_str, bit);
free (bit);
bit = NULL;
}
*state->cdm_str = ctf_str_append (*state->cdm_str, ")\n");
*state->cdm_str = str_append (*state->cdm_str, ")\n");
return 0;
oom:
@ -593,7 +595,7 @@ ctf_dump_type (ctf_id_t id, int flag, void *arg)
goto err;
}
str = ctf_str_append (str, "\n");
str = str_append (str, "\n");
if ((ctf_type_visit (state->cds_fp, id, ctf_dump_member, &membstate)) < 0)
{
if (id == 0 || ctf_errno (state->cds_fp) == ECTF_NONREPRESENTABLE)
@ -752,8 +754,8 @@ ctf_dump (ctf_file_t *fp, ctf_dump_state_t **statep, ctf_sect_names_t sect,
nline[0] = '\0';
ret = func (sect, line, arg);
str = ctf_str_append (str, ret);
str = ctf_str_append (str, "\n");
str = str_append (str, ret);
str = str_append (str, "\n");
if (ret != line)
free (ret);
@ -772,7 +774,14 @@ ctf_dump (ctf_file_t *fp, ctf_dump_state_t **statep, ctf_sect_names_t sect,
str[len-1] = '\0';
}
else
str = strdup (state->cds_current->cdi_item);
{
str = strdup (state->cds_current->cdi_item);
if (!str)
{
ctf_set_errno (fp, ENOMEM);
return str;
}
}
ctf_set_errno (fp, 0);
return str;

1
libctf/ctf-impl.h
View File

@ -457,6 +457,7 @@ extern ssize_t ctf_pread (int fd, void *buf, ssize_t count, off_t offset);
extern void *ctf_realloc (ctf_file_t *, void *, size_t);
extern char *ctf_str_append (char *, const char *);
extern char *ctf_str_append_noerr (char *, const char *);
extern const char *ctf_strerror (int);
extern ctf_id_t ctf_type_resolve_unsliced (ctf_file_t *, ctf_id_t);

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)