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exec: let do_coredump() limit the number of concurrent dumps to pipes

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Introduce core pipe limiting sysctl.

Since we can dump cores to pipe, rather than directly to the filesystem,
we create a condition in which a user can create a very high load on the
system simply by running bad applications.

If the pipe reader specified in core_pattern is poorly written, we can
have lots of ourstandig resources and processes in the system.

This sysctl introduces an ability to limit that resource consumption.
core_pipe_limit defines how many in-flight dumps may be run in parallel,
dumps beyond this value are skipped and a note is made in the kernel log.
A special value of 0 in core_pipe_limit denotes unlimited core dumps may
be handled (this is the default value).

[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 15:56:56 -07:00
committed by Linus Torvalds
parent 725eae32df
commit a293980c2e
3 changed files with 49 additions and 5 deletions
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23
fs/exec.c
View File

@@ -63,6 +63,7 @@
int core_uses_pid;
char core_pattern[CORENAME_MAX_SIZE] = "core";
unsigned int core_pipe_limit;
int suid_dumpable = 0;
/* The maximal length of core_pattern is also specified in sysctl.c */
@@ -1744,7 +1745,8 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
char **helper_argv = NULL;
int helper_argc = 0;
char *delimit;
int dump_count = 0;
static atomic_t core_dump_count = ATOMIC_INIT(0);
audit_core_dumps(signr);
@@ -1826,28 +1828,36 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
goto fail_unlock;
}
dump_count = atomic_inc_return(&core_dump_count);
if (core_pipe_limit && (core_pipe_limit < dump_count)) {
printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
task_tgid_vnr(current), current->comm);
printk(KERN_WARNING "Skipping core dump\n");
goto fail_dropcount;
}
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;
goto fail_dropcount;
}
core_limit = RLIM_INFINITY;
/* SIGPIPE can happen, but it's just never processed */
if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL,
&file)) {
printk(KERN_INFO "Core dump to %s pipe failed\n",
corename);
goto fail_unlock;
goto fail_dropcount;
}
} else
file = filp_open(corename,
O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
0600);
if (IS_ERR(file))
goto fail_unlock;
goto fail_dropcount;
inode = file->f_path.dentry->d_inode;
if (inode->i_nlink > 1)
goto close_fail; /* multiple links - don't dump */
@@ -1877,6 +1887,9 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
current->signal->group_exit_code |= 0x80;
close_fail:
filp_close(file, NULL);
fail_dropcount:
if (dump_count)
atomic_dec(&core_dump_count);
fail_unlock:
if (helper_argv)
argv_free(helper_argv);