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exec: make do_coredump() more resilient to recursive crashes 

Change how we detect recursive dumps.

Currently we have a mechanism by which we try to compare pathnames of the
crashing process to the core_pattern path.  This is broken for a dozen
reasons, and just doesn't work in any sort of robust way.

I'm replacing it with the use of a 0 RLIMIT_CORE value.  Since helper apps
set RLIMIT_CORE to zero, we don't write out core files for any process
with that particular limit set.  It the core_pattern is a pipe, any
non-zero limit is translated to RLIM_INFINITY.

This allows complete dumps to be captured, but prevents infinite recursion
in the event that the core_pattern process itself crashes.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Earl Chew <earl_chew@agilent.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Neil Horman 2009-09-23 15:56:54 -07:00 committed by Linus Torvalds
parent ae6d2ed7bb
commit 725eae32df
1 changed files with 23 additions and 22 deletions
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45
fs/exec.c
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@ -1799,38 +1799,39 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
lock_kernel();
ispipe = format_corename(corename, signr);
unlock_kernel();
/*
* Don't bother to check the RLIMIT_CORE value if core_pattern points
* to a pipe. Since we're not writing directly to the filesystem
* RLIMIT_CORE doesn't really apply, as no actual core file will be
* created unless the pipe reader choses to write out the core file
* 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))
goto fail_unlock;
if (ispipe) {
if (core_limit == 0) {
/*
* Normally core limits are irrelevant to pipes, since
* we're not writing to the file system, but we use
* core_limit of 0 here as a speacial value. Any
* non-zero limit gets set to RLIM_INFINITY below, but
* a limit of 0 skips the dump. This is a consistent
* way to catch recursive crashes. We can still crash
* if the core_pattern binary sets RLIM_CORE = !0
* but it runs as root, and can do lots of stupid things
* Note that we use task_tgid_vnr here to grab the pid
* of the process group leader. That way we get the
* right pid if a thread in a multi-threaded
* core_pattern process dies.
*/
printk(KERN_WARNING
"Process %d(%s) has RLIMIT_CORE set to 0\n",
task_tgid_vnr(current), current->comm);
printk(KERN_WARNING "Aborting core\n");
goto fail_unlock;
}
helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
if (!helper_argv) {
printk(KERN_WARNING "%s failed to allocate memory\n",
__func__);
goto fail_unlock;
}
/* Terminate the string before the first option */
delimit = strchr(corename, ' ');
if (delimit)
*delimit = '\0';
delimit = strrchr(helper_argv[0], '/');
if (delimit)
delimit++;
else
delimit = helper_argv[0];
if (!strcmp(delimit, current->comm)) {
printk(KERN_NOTICE "Recursive core dump detected, "
"aborting\n");
goto fail_unlock;
}
core_limit = RLIM_INFINITY;