linux-stable.git/fs/proc/generic.c, branch v5.12

fs: make helpers idmap mount aware

2021-01-24T13:27:20+00:00

Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig 
Cc: David Howells 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner

stat: handle idmapped mounts

2021-01-24T13:27:17+00:00

The generic_fillattr() helper fills in the basic attributes associated
with an inode. Enable it to handle idmapped mounts. If the inode is
accessed through an idmapped mount map it into the mount's user
namespace before we store the uid and gid. If the initial user namespace
is passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-12-christian.brauner@ubuntu.com
Cc: Christoph Hellwig 
Cc: David Howells 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Reviewed-by: James Morris 
Signed-off-by: Christian Brauner

attr: handle idmapped mounts

2021-01-24T13:27:16+00:00

When file attributes are changed most filesystems rely on the
setattr_prepare(), setattr_copy(), and notify_change() helpers for
initialization and permission checking. Let them handle idmapped mounts.
If the inode is accessed through an idmapped mount map it into the
mount's user namespace. Afterwards the checks are identical to
non-idmapped mounts. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Helpers that perform checks on the ia_uid and ia_gid fields in struct
iattr assume that ia_uid and ia_gid are intended values and have already
been mapped correctly at the userspace-kernelspace boundary as we
already do today. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com
Cc: Christoph Hellwig 
Cc: David Howells 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner

proc: fix lookup in /proc/net subdirectories after setns(2)

2020-12-16T06:46:15+00:00

Commit 1fde6f21d90f ("proc: fix /proc/net/* after setns(2)") only forced
revalidation of regular files under /proc/net/

However, /proc/net/ is unusual in the sense of /proc/net/foo handlers
take netns pointer from parent directory which is old netns.

Steps to reproduce:

	(void)open("/proc/net/sctp/snmp", O_RDONLY);
	unshare(CLONE_NEWNET);

	int fd = open("/proc/net/sctp/snmp", O_RDONLY);
	read(fd, &c, 1);

Read will read wrong data from original netns.

Patch forces lookup on every directory under /proc/net .

Link: https://lkml.kernel.org/r/20201205160916.GA109739@localhost.localdomain
Fixes: 1da4d377f943 ("proc: revalidate misc dentries")
Signed-off-by: Alexey Dobriyan 
Reported-by: "Rantala, Tommi T. (Nokia - FI/Espoo)" 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

proc "seq files": switch to ->read_iter

2020-11-06T18:05:18+00:00

Implement ->read_iter for all proc "seq files" so that splice works on
them.

Suggested-by: Linus Torvalds 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Linus Torvalds

proc "single files": switch to ->read_iter

2020-11-06T18:05:18+00:00

Implement ->read_iter for all proc "single files" so that more bionic
tests cases can pass when they call splice() on other fun files like
/proc/version

Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Linus Torvalds

proc: add option to mount only a pids subset

2020-04-22T15:51:22+00:00

This allows to hide all files and directories in the procfs that are not
related to tasks.

Signed-off-by: Alexey Gladkov 
Reviewed-by: Alexey Dobriyan 
Reviewed-by: Kees Cook 
Signed-off-by: Eric W. Biederman

proc: faster open/read/close with "permanent" files

2020-04-07T17:43:42+00:00

Now that "struct proc_ops" exist we can start putting there stuff which
could not fly with VFS "struct file_operations"...

Most of fs/proc/inode.c file is dedicated to make open/read/.../close
reliable in the event of disappearing /proc entries which usually happens
if module is getting removed.  Files like /proc/cpuinfo which never
disappear simply do not need such protection.

Save 2 atomic ops, 1 allocation, 1 free per open/read/close sequence for such
"permanent" files.

Enable "permanent" flag for

	/proc/cpuinfo
	/proc/kmsg
	/proc/modules
	/proc/slabinfo
	/proc/stat
	/proc/sysvipc/*
	/proc/swaps

More will come once I figure out foolproof way to prevent out module
authors from marking their stuff "permanent" for performance reasons
when it is not.

This should help with scalability: benchmark is "read /proc/cpuinfo R times
by N threads scattered over the system".

	N	R	t, s (before)	t, s (after)
	-----------------------------------------------------
	64	4096	1.582458	1.530502	-3.2%
	256	4096	6.371926	6.125168	-3.9%
	1024	4096	25.64888	24.47528	-4.6%

Benchmark source:

#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 

const int NR_CPUS = sysconf(_SC_NPROCESSORS_ONLN);
int N;
const char *filename;
int R;

int xxx = 0;

int glue(int n)
{
	cpu_set_t m;
	CPU_ZERO(&m);
	CPU_SET(n, &m);
	return sched_setaffinity(0, sizeof(cpu_set_t), &m);
}

void f(int n)
{
	glue(n % NR_CPUS);

	while (*(volatile int *)&xxx == 0) {
	}

	for (int i = 0; i < R; i++) {
		int fd = open(filename, O_RDONLY);
		char buf[4096];
		ssize_t rv = read(fd, buf, sizeof(buf));
		asm volatile ("" :: "g" (rv));
		close(fd);
	}
}

int main(int argc, char *argv[])
{
	if (argc < 4) {
		std::cerr << "usage: " << argv[0] << ' ' << "N /proc/filename R
";
		return 1;
	}

	N = atoi(argv[1]);
	filename = argv[2];
	R = atoi(argv[3]);

	for (int i = 0; i < NR_CPUS; i++) {
		if (glue(i) == 0)
			break;
	}

	std::vector T;
	T.reserve(N);
	for (int i = 0; i < N; i++) {
		T.emplace_back(f, i);
	}

	auto t0 = std::chrono::system_clock::now();
	{
		*(volatile int *)&xxx = 1;
		for (auto& t: T) {
			t.join();
		}
	}
	auto t1 = std::chrono::system_clock::now();
	std::chrono::duration dt = t1 - t0;
	std::cout << dt.count() << '
';

	return 0;
}

P.S.:
Explicit randomization marker is added because adding non-function pointer
will silently disable structure layout randomization.

[akpm@linux-foundation.org: coding style fixes]
Reported-by: kbuild test robot 
Reported-by: Dan Carpenter 
Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Cc: Al Viro 
Cc: Joe Perches 
Link: http://lkml.kernel.org/r/20200222201539.GA22576@avx2
Signed-off-by: Linus Torvalds

proc: decouple proc from VFS with "struct proc_ops"

2020-02-04T03:05:26+00:00

Currently core /proc code uses "struct file_operations" for custom hooks,
however, VFS doesn't directly call them.  Every time VFS expands
file_operations hook set, /proc code bloats for no reason.

Introduce "struct proc_ops" which contains only those hooks which /proc
allows to call into (open, release, read, write, ioctl, mmap, poll).  It
doesn't contain module pointer as well.

Save ~184 bytes per usage:

	add/remove: 26/26 grow/shrink: 1/4 up/down: 1922/-6674 (-4752)
	Function                                     old     new   delta
	sysvipc_proc_ops                               -      72     +72
				...
	config_gz_proc_ops                             -      72     +72
	proc_get_inode                               289     339     +50
	proc_reg_get_unmapped_area                   110     107      -3
	close_pdeo                                   227     224      -3
	proc_reg_open                                289     284      -5
	proc_create_data                              60      53      -7
	rt_cpu_seq_fops                              256       -    -256
				...
	default_affinity_proc_fops                   256       -    -256
	Total: Before=5430095, After=5425343, chg -0.09%

Link: http://lkml.kernel.org/r/20191225172228.GA13378@avx2
Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs/proc/generic.c: delete useless "len" variable

2019-12-05T03:44:11+00:00

Pointer to next '/' encodes length of path element and next start
position.  Subtraction and increment are redundant.

Link: http://lkml.kernel.org/r/20191004234521.GA30246@avx2
Signed-off-by: Alexey Dobriyan 
Reviewed-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds