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coredump: protect corefilename access with a lock

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Previously format string traversal could happen while the string itself was
being modified.

Use allproc_lock as coredumping is a rare operation and as such we don't
have to create a dedicated lock.

Submitted by:	Tiwei Bie <btw mail.ustc.edu.cn>
Reviewed by:	kib
X-Additional:	JuniorJobs project
This commit is contained in:
Mateusz Guzik 2015-03-21 04:39:33 +00:00
parent febd9e9c94
commit 5bc0ff888a
1 changed files with 23 additions and 2 deletions
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25
sys/kern/kern_sig.c
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@ -3089,9 +3089,28 @@ SYSCTL_INT(_kern, OID_AUTO, compress_user_cores_gzlevel, CTLFLAG_RWTUN,
static int compress_user_cores = 0;
#endif
/*
* Protect the access to corefilename[] by allproc_lock.
*/
#define corefilename_lock allproc_lock
static char corefilename[MAXPATHLEN] = {"%N.core"};
SYSCTL_STRING(_kern, OID_AUTO, corefile, CTLFLAG_RWTUN, corefilename,
sizeof(corefilename), "Process corefile name format string");
static int
sysctl_kern_corefile(SYSCTL_HANDLER_ARGS)
{
int error;
sx_xlock(&corefilename_lock);
error = sysctl_handle_string(oidp, corefilename, sizeof(corefilename),
req);
sx_xunlock(&corefilename_lock);
return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, corefile, CTLTYPE_STRING | CTLFLAG_RWTUN |
CTLFLAG_MPSAFE, 0, 0, sysctl_kern_corefile, "A",
"Process corefile name format string");
/*
* corefile_open(comm, uid, pid, td, compress, vpp, namep)
@ -3120,6 +3139,7 @@ corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
name = malloc(MAXPATHLEN, M_TEMP, M_WAITOK | M_ZERO);
indexpos = -1;
(void)sbuf_new(&sb, name, MAXPATHLEN, SBUF_FIXEDLEN);
sx_slock(&corefilename_lock);
for (i = 0; format[i] != '\0'; i++) {
switch (format[i]) {
case '%': /* Format character */
@ -3162,6 +3182,7 @@ corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
break;
}
}
sx_sunlock(&corefilename_lock);
free(hostname, M_TEMP);
if (compress)
sbuf_printf(&sb, GZ_SUFFIX);