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Date:      Wed, 25 Mar 2015 14:00:12 +0800
From:      Tiwei Bie <btw@mail.ustc.edu.cn>
To:        Mateusz Guzik <mjguzik@gmail.com>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, freebsd-hackers@freebsd.org
Subject:   Re: [PATCH] Finish the task 'Validate coredump format string'
Message-ID:  <20150325060012.GA75674@freebsd>
In-Reply-To: <20150324143709.GA54065@freebsd>
References:  <20150322091853.GA89976@freebsd> <20150322101401.GH14650@dft-labs.eu> <20150322112555.GA44277@freebsd> <20150322113822.GB2379@kib.kiev.ua> <20150322120655.GA59757@freebsd> <20150322131524.GA95795@freebsd> <20150323005852.GB6798@dft-labs.eu> <20150323020314.GA30143@freebsd> <20150324123517.GA25678@dft-labs.eu> <20150324143709.GA54065@freebsd>

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On Tue, Mar 24, 2015 at 10:37:09PM +0800, Tiwei Bie wrote:
> On Tue, Mar 24, 2015 at 01:35:17PM +0100, Mateusz Guzik wrote:
> > On Mon, Mar 23, 2015 at 10:03:14AM +0800, Tiwei Bie wrote:
> > > On Mon, Mar 23, 2015 at 01:58:52AM +0100, Mateusz Guzik wrote:
> > > > On Sun, Mar 22, 2015 at 09:15:24PM +0800, Tiwei Bie wrote:
> > > > > On Sun, Mar 22, 2015 at 08:06:55PM +0800, Tiwei Bie wrote:
> > > > > > On Sun, Mar 22, 2015 at 01:38:22PM +0200, Konstantin Belousov wrote:
> > > > > > > On Sun, Mar 22, 2015 at 07:25:55PM +0800, Tiwei Bie wrote:
> > > > > > > > On Sun, Mar 22, 2015 at 11:14:01AM +0100, Mateusz Guzik wrote:
> > > > > > > > > On Sun, Mar 22, 2015 at 05:19:40PM +0800, Tiwei Bie wrote:
> > > 
[..]
> +static void
> +corefilename_init(void *arg)
> +{
> +	char *format;
> +
> +	format = kern_getenv("kern.corefile");
> +	if (format == NULL)
> +		return;
> +
> +	if (corefilename_check(format))
> +		strcpy(corefilename, format);
> +	else
> +		printf("Invalid format character specified in "
> +		    "corename `%s'\n", format);
> +

The message printed in corefilename_init() is not proper, it doesn't
cover the case that the length is too long, nor the case that %I is
specified more than once. I extended the corefilename_check() to be
able to return the reason (error code) if it fails. But I'm not sure
whether it is worthwhile, cause it seems currently there is no way to
specified a string longer than MAXPATHLEN via sysctl or kenv.

I also removed the '\n' character from KASSERT() in corefile_open(),
as what the other codes do.

Here is my new patch:

---
 share/man/man5/core.5 |  7 ++++
 sys/kern/kern_sig.c   | 93 +++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 93 insertions(+), 7 deletions(-)

diff --git a/share/man/man5/core.5 b/share/man/man5/core.5
index 3f54f89..3047e0a 100644
--- a/share/man/man5/core.5
+++ b/share/man/man5/core.5
@@ -78,6 +78,7 @@ An index starting at zero until the sysctl
 is reached.
 This can be useful for limiting the number of corefiles
 generated by a particular process.
+This specifier can only be specified at most once.
 .It Em \&%N
 process name.
 .It Em \&%P
@@ -91,6 +92,12 @@ The name defaults to
 yielding the traditional
 .Fx
 behaviour.
+When changing the name via the
+.Va kern.corefile
+sysctl, it will fail if the new name contains
+unknown format specifiers, or
+.Em \&%I
+is specified more than once, or its length is too long.
 .Pp
 By default, a process that changes user or group credentials whether
 real or effective will not create a corefile.
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 154c250..7fdb079 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -3094,21 +3094,101 @@ static int compress_user_cores = 0;
  */
 #define	corefilename_lock	allproc_lock
 
-static char corefilename[MAXPATHLEN] = {"%N.core"};
+static char corefilename[MAXPATHLEN] = "%N.core";
+
+static int
+corefilename_check(const char *format)
+{
+	int i, countI;
+
+	countI = 0;
+	for (i = 0; i < MAXPATHLEN && format[i] != '\0'; i++) {
+		if (format[i] == '%') {
+			i++;
+			switch (format[i]) {
+			case 'I':
+				countI++;
+				if (countI > 1)
+					return (EINVAL);
+			case '%':
+			case 'H':
+			case 'N':
+			case 'P':
+			case 'U':
+				break;
+			default:
+				return (EINVAL);
+			}
+		}
+	}
+
+	if (i == MAXPATHLEN)
+		return (ENAMETOOLONG);
+
+	return (0);
+}
+
+static void
+corefilename_init(void *arg)
+{
+	char *format;
+	int error;
+
+	format = kern_getenv("kern.corefile");
+	if (format == NULL)
+		return;
+
+	error = corefilename_check(format);
+
+	switch (error) {
+	case 0:
+		strcpy(corefilename, format);
+		break;
+	case EINVAL:
+		printf("Invalid format specified for corename `%s'\n", format);
+		break;
+	case ENAMETOOLONG:
+		printf("The format specified for corename is too long\n");
+		break;
+	default:
+		KASSERT(0, ("%s: unknown return value %d from "
+		    "corefilename_check", __func__, error));
+		break;
+	}
+
+	freeenv(format);
+}
+SYSINIT(corefilename, SI_SUB_KMEM, SI_ORDER_FIRST, corefilename_init, 0);
 
 static int
 sysctl_kern_corefile(SYSCTL_HANDLER_ARGS)
 {
+	char *format;
 	int error;
 
+	format = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
+
+	sx_slock(&corefilename_lock);
+	strcpy(format, corefilename);
+	sx_sunlock(&corefilename_lock);
+
+	error = sysctl_handle_string(oidp, format, MAXPATHLEN, req);
+	if (error != 0 || req->newptr == NULL)
+		goto out;
+
+	error = corefilename_check(format);
+	if (error != 0)
+		goto out;
+
 	sx_xlock(&corefilename_lock);
-	error = sysctl_handle_string(oidp, corefilename, sizeof(corefilename),
-	    req);
+	strcpy(corefilename, format);
 	sx_xunlock(&corefilename_lock);
 
+out:
+	free(format, M_TEMP);
 	return (error);
 }
-SYSCTL_PROC(_kern, OID_AUTO, corefile, CTLTYPE_STRING | CTLFLAG_RWTUN |
+SYSCTL_PROC(_kern, OID_AUTO, corefile, CTLTYPE_STRING | CTLFLAG_RW |
     CTLFLAG_MPSAFE, 0, 0, sysctl_kern_corefile, "A",
     "Process corefile name format string");
 
@@ -3171,9 +3251,8 @@ corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
 				sbuf_printf(&sb, "%u", uid);
 				break;
 			default:
-				log(LOG_ERR,
-				    "Unknown format character %c in "
-				    "corename `%s'\n", format[i], format);
+				KASSERT(0, ("Unknown format character %c in "
+				    "corename `%s'", format[i], format));
 				break;
 			}
 			break;
-- 
2.1.2

Best regards,
Tiwei Bie




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