/*
 * Naive system call dropper built on seccomp_filter.
 *
 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
 * Author: Will Drewry <wad@chromium.org>
 *
 * The code may be used by anyone for any purpose,
 * and can serve as a starting point for developing
 * applications using prctl(PR_SET_SECCOMP, 2, ...).
 *
 * When run, returns the specified errno for the specified
 * system call number against the given architecture.
 *
 */

#include <errno.h>
#include <linux/audit.h>
#include <linux/filter.h>
#include <linux/seccomp.h>
#include <linux/unistd.h>
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <sys/prctl.h>
#include <unistd.h>

static int install_filter(int nr, int arch, int error)
{
	struct sock_filter filter[] = {
		BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
			 (offsetof(struct seccomp_data, arch))),
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, arch, 0, 3),
		BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
			 (offsetof(struct seccomp_data, nr))),
		BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, nr, 0, 1),
		BPF_STMT(BPF_RET+BPF_K,
			 SECCOMP_RET_ERRNO|(error & SECCOMP_RET_DATA)),
		BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
	};
	struct sock_fprog prog = {
		.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
		.filter = filter,
	};
	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
		perror("prctl(NO_NEW_PRIVS)");
		return 1;
	}
	if (prctl(PR_SET_SECCOMP, 2, &prog)) {
		perror("prctl(PR_SET_SECCOMP)");
		return 1;
	}
	return 0;
}

int main(int argc, char **argv)
{
	if (argc < 5) {
		fprintf(stderr, "Usage:\n"
			"dropper <syscall_nr> <arch> <errno> <prog> [<args>]\n"
			"Hint:	AUDIT_ARCH_I386: 0x%X\n"
			"	AUDIT_ARCH_X86_64: 0x%X\n"
			"\n", AUDIT_ARCH_I386, AUDIT_ARCH_X86_64);
		return 1;
	}
	if (install_filter(strtol(argv[1], NULL, 0), strtol(argv[2], NULL, 0),
			   strtol(argv[3], NULL, 0)))
		return 1;
	execv(argv[4], &argv[4]);
	printf("Failed to execv\n");
	return 255;
}
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/commit/?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/include?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>include</a>/<a href='/cgit.cgi/linux/net-next.git/commit/include/dt-bindings?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>dt-bindings</a>/<a href='/cgit.cgi/linux/net-next.git/commit/include/dt-bindings/dma?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>dma</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='3895dbf8985f656675b5bde610723a29cbce3fa7'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Eric W. Biederman &lt;ebiederm@xmission.com&gt;</td><td class='right'>2017-01-03 14:18:43 +1300</td></tr>
<tr><th>committer</th><td>Eric W. Biederman &lt;ebiederm@xmission.com&gt;</td><td class='right'>2017-01-10 13:34:43 +1300</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/dt-bindings/dma?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>3895dbf8985f656675b5bde610723a29cbce3fa7</a> (<a href='/cgit.cgi/linux/net-next.git/patch/include/dt-bindings/dma?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>91d4517f09918fd573998eb40b8f35f08ed1c470</a> /<a href='/cgit.cgi/linux/net-next.git/tree/include/dt-bindings/dma?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>include/dt-bindings/dma</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/dt-bindings/dma?id=0c744ea4f77d72b3dcebb7a8f2684633ec79be88'>0c744ea4f77d72b3dcebb7a8f2684633ec79be88</a> (<a href='/cgit.cgi/linux/net-next.git/diff/include/dt-bindings/dma?id=3895dbf8985f656675b5bde610723a29cbce3fa7&amp;id2=0c744ea4f77d72b3dcebb7a8f2684633ec79be88'>diff</a>)</td></tr></table>
<div class='commit-subject'>mnt: Protect the mountpoint hashtable with mount_lock</div><div class='commit-msg'>Protecting the mountpoint hashtable with namespace_sem was sufficient
until a call to umount_mnt was added to mntput_no_expire.  At which
point it became possible for multiple calls of put_mountpoint on
the same hash chain to happen on the same time.

Kristen Johansen &lt;kjlx@templeofstupid.com&gt; reported:
&gt; This can cause a panic when simultaneous callers of put_mountpoint
&gt; attempt to free the same mountpoint.  This occurs because some callers
&gt; hold the mount_hash_lock, while others hold the namespace lock.  Some
&gt; even hold both.
&gt;
&gt; In this submitter's case, the panic manifested itself as a GP fault in
&gt; put_mountpoint() when it called hlist_del() and attempted to dereference
&gt; a m_hash.pprev that had been poisioned by another thread.

Al Viro observed that the simple fix is to switch from using the namespace_sem
to the mount_lock to protect the mountpoint hash table.

I have taken Al's suggested patch moved put_mountpoint in pivot_root
(instead of taking mount_lock an additional time), and have replaced
new_mountpoint with get_mountpoint a function that does the hash table
lookup and addition under the mount_lock.   The introduction of get_mounptoint
ensures that only the mount_lock is needed to manipulate the mountpoint
hashtable.

d_set_mounted is modified to only set DCACHE_MOUNTED if it is not
already set.  This allows get_mountpoint to use the setting of
DCACHE_MOUNTED to ensure adding a struct mountpoint for a dentry
happens exactly once.

Cc: stable@vger.kernel.org
Fixes: ce07d891a089 ("mnt: Honor MNT_LOCKED when detaching mounts")
Reported-by: Krister Johansen &lt;kjlx@templeofstupid.com&gt;
Suggested-by: Al Viro &lt;viro@ZenIV.linux.org.uk&gt;
Acked-by: Al Viro &lt;viro@ZenIV.linux.org.uk&gt;
Signed-off-by: "Eric W. Biederman" &lt;ebiederm@xmission.com&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=3895dbf8985f656675b5bde610723a29cbce3fa7'>Diffstat</a> (limited to 'include/dt-bindings/dma')</div><table summary='diffstat' class='diffstat'>