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Subject[PATCH] core_pattern: Add ability for core_pattern to parse arguments when pattern is a pipe
Hey-
Currently, core dumps can be redirected to a pipe by placing the
following string template in /proc/sys/kernel/core_pattern:
|<path/to/application>
This patch extends this ability, allowing the core_pattern to contain arguments
to be passed as an argv array to the userspace helper application. It also add
a format specifier, %c, which allows the RLIM_CORE value of the crashing
application to be passed on the command line, since RLIMIT_CORE is reduced to
zero when execing the userspace helper

Tested successfully by me on x86 & x86_64.

Regards
Neil

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>


exec.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 119 insertions(+), 3 deletions(-)


diff --git a/fs/exec.c b/fs/exec.c
index c0b5def..e862019 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -51,6 +51,7 @@
#include <linux/cn_proc.h>
#include <linux/audit.h>
#include <linux/signalfd.h>
+#include <linux/string.h>

#include <asm/uaccess.h>
#include <asm/mmu_context.h>
@@ -1448,6 +1449,109 @@ int set_binfmt(struct linux_binfmt *new)

EXPORT_SYMBOL(set_binfmt);

+static void free_argv_array(char **argv)
+{
+ int i;
+ if (argv != NULL) {
+ for (i = 0; argv[i] != NULL; i++)
+ kfree(argv[i]);
+ kfree(argv);
+ }
+
+}
+
+/*
+ * format_corename_argv will inspect the corename string,
+ * and for every option found after the binary name
+ * it will remove the option from the string, and place it
+ * in the argv array, that can then be passed to the
+ * usermodehelper if core_pattern is a pipe
+ * Assumes that corename is declared on the stack of the caller
+ */
+static char **format_corename_argv(char *corename)
+{
+ char *nptr = corename;
+ char *fptr = NULL;
+ char **orig_argv;
+ char **argv_ptr;
+ int i = 2;
+
+ /*
+ * Start by populating element 0 with the name of the binary
+ */
+ argv_ptr = kmalloc(sizeof(char **)*i, GFP_KERNEL);
+ if (!argv_ptr)
+ goto out;
+ orig_argv = argv_ptr;
+
+ argv_ptr[0] = NULL;
+ argv_ptr[1] = NULL;
+ fptr = strchr(nptr, ' ');
+
+ /* This trucates the string command line for use in exec */
+ if (fptr != NULL)
+ *fptr = '\0';
+
+ nptr = nptr + 1; /*this removes the leading | */
+ argv_ptr[0] = kmalloc(strlen(nptr), GFP_KERNEL);
+ if (argv_ptr[0] == NULL)
+ goto out_free;
+
+ strcpy(argv_ptr[0], nptr);
+
+ /*
+ * This handles the case where we have no options
+ */
+ if (fptr == NULL)
+ goto out;
+ /*
+ * Now walk through the rest of the corename with nptr and
+ * fptr, delimiting by spaces and filling out the array
+ */
+ nptr = fptr + 1;
+ for(;;) {
+ fptr = strchr(nptr, ' ');
+
+ /*
+ * Found a new option, lets add to the array
+ */
+ argv_ptr = krealloc(argv_ptr, (sizeof(char **)*(i+1)), GFP_KERNEL);
+ if (!argv_ptr)
+ goto out_free;
+
+ argv_ptr[i] = NULL; /* set the end of the array to NULL */
+ if (fptr != NULL)
+ *fptr = '\0';
+
+ argv_ptr[i-1] = kmalloc(strlen(nptr), GFP_KERNEL);
+ if (argv_ptr[i-1] == NULL)
+ goto out_free;
+
+ /*
+ * copy the option and advance our pointers
+ */
+ strcpy(argv_ptr[i-1],nptr);
+ if (fptr == NULL)
+ break;
+ i++;
+ nptr = fptr + 1;
+ }
+
+
+ /*
+ * now we have our array built
+ */
+ return argv_ptr;
+
+out_free:
+ for (i = 0;orig_argv[i] != NULL; i++)
+ kfree(orig_argv[i]);
+ kfree(orig_argv);
+ argv_ptr = NULL;
+out:
+ return argv_ptr;
+}
+
/* format_corename will inspect the pattern parameter, and output a
* name into corename, which must have space for at least
* CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
@@ -1543,6 +1647,14 @@ static int format_corename(char *corename, const char *pattern, long signr)
goto out;
out_ptr += rc;
break;
+ /* core limit size */
+ case 'c':
+ rc = snprintf(out_ptr, out_end - out_ptr,
+ "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
+ if (rc > out_end - out_ptr)
+ goto out;
+ out_ptr += rc;
+ break;
default:
break;
}
@@ -1727,6 +1839,7 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
int flag = 0;
int ispipe = 0;
unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
+ char **helper_argv = NULL;

audit_core_dumps(signr);

@@ -1775,14 +1888,14 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
* at which point file size limits and permissions will be imposed
* as it does with any other process
*/
- if ((!ispipe) &&
- (core_limit < binfmt->min_coredump))
+ if ((!ispipe) && (core_limit < binfmt->min_coredump))
goto fail_unlock;

if (ispipe) {
core_limit = RLIM_INFINITY;
+ helper_argv = format_corename_argv(corename);
/* SIGPIPE can happen, but it's just never processed */
- if(call_usermodehelper_pipe(corename+1, NULL, NULL, &file)) {
+ if(call_usermodehelper_pipe(corename+1, helper_argv, NULL, &file)) {
printk(KERN_INFO "Core dump to %s pipe failed\n",
corename);
goto fail_unlock;
@@ -1817,6 +1930,9 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
close_fail:
filp_close(file, NULL);
fail_unlock:
+ if (ispipe)
+ free_argv_array(helper_argv);
+
current->fsuid = fsuid;
complete_all(&mm->core_done);
fail:
--
/***************************************************
*Neil Horman
*Software Engineer
*Red Hat, Inc.
*nhorman@tuxdriver.com
*gpg keyid: 1024D / 0x92A74FA1
*http://pgp.mit.edu
***************************************************/
-
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