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Alexey Dobriyan ea5c294432 proc: fix coredump vs read /proc/*/stat race 
commit 8bb2ee192e482c5d500df9f2b1b26a560bd3026f upstream.

do_task_stat() accesses IP and SP of a task without bumping reference
count of a stack (which became an entity with independent lifetime at
some point).

Steps to reproduce:

    #include <stdio.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <sys/time.h>
    #include <sys/resource.h>
    #include <unistd.h>
    #include <sys/wait.h>

    int main(void)
    {
    	setrlimit(RLIMIT_CORE, &(struct rlimit){});

    	while (1) {
    		char buf[64];
    		char buf2[4096];
    		pid_t pid;
    		int fd;

    		pid = fork();
    		if (pid == 0) {
    			*(volatile int *)0 = 0;
    		}

    		snprintf(buf, sizeof(buf), "/proc/%u/stat", pid);
    		fd = open(buf, O_RDONLY);
    		read(fd, buf2, sizeof(buf2));
    		close(fd);

    		waitpid(pid, NULL, 0);
    	}
    	return 0;
    }

    BUG: unable to handle kernel paging request at 0000000000003fd8
    IP: do_task_stat+0x8b4/0xaf0
    PGD 800000003d73e067 P4D 800000003d73e067 PUD 3d558067 PMD 0
    Oops: 0000 [#1] PREEMPT SMP PTI
    CPU: 0 PID: 1417 Comm: a.out Not tainted 4.15.0-rc8-dirty #2
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc27 04/01/2014
    RIP: 0010:do_task_stat+0x8b4/0xaf0
    Call Trace:
     proc_single_show+0x43/0x70
     seq_read+0xe6/0x3b0
     __vfs_read+0x1e/0x120
     vfs_read+0x84/0x110
     SyS_read+0x3d/0xa0
     entry_SYSCALL_64_fastpath+0x13/0x6c
    RIP: 0033:0x7f4d7928cba0
    RSP: 002b:00007ffddb245158 EFLAGS: 00000246
    Code: 03 b7 a0 01 00 00 4c 8b 4c 24 70 4c 8b 44 24 78 4c 89 74 24 18 e9 91 f9 ff ff f6 45 4d 02 0f 84 fd f7 ff ff 48 8b 45 40 48 89 ef <48> 8b 80 d8 3f 00 00 48 89 44 24 20 e8 9b 97 eb ff 48 89 44 24
    RIP: do_task_stat+0x8b4/0xaf0 RSP: ffffc90000607cc8
    CR2: 0000000000003fd8

John Ogness said: for my tests I added an else case to verify that the
race is hit and correctly mitigated.

Link: http://lkml.kernel.org/r/20180116175054.GA11513@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: "Kohli, Gaurav" <gkohli@codeaurora.org>
Tested-by: John Ogness <john.ogness@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-01-23 19:58:18 +01:00
..
9p
fs/9p: Compare qid.path in v9fs_test_inode
2017-11-30 08:40:49 +00:00
adfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
affs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
afs
afs: Connect up the CB.ProbeUuid
2017-12-14 09:53:15 +01:00
autofs4
autofs: fix careless error in recent commit
2017-12-20 10:10:17 +01:00
befs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
bfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
btrfs
btrfs: fix refcount_t usage when deleting btrfs_delayed_nodes
2018-01-10 09:31:17 +01:00
cachefiles
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
ceph
ceph: drop negative child dentries before try pruning inode's alias
2017-12-20 10:10:19 +01:00
cifs
cifs: fix NULL deref in SMB2_read
2017-12-20 10:10:17 +01:00
coda
coda: fix 'kernel memory exposure attempt' in fsync
2017-11-24 08:37:05 +01:00
configfs
…
cramfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
crypto
fscrypt: lock mutex before checking for bounce page pool
2017-11-30 08:40:44 +00:00
debugfs
Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2017-07-15 12:00:42 -07:00
devpts
pty: Repair TIOCGPTPEER
2017-08-24 13:23:03 -07:00
dlm
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
ecryptfs
eCryptfs: use after free in ecryptfs_release_messaging()
2017-11-30 08:40:45 +00:00
efivarfs
VFS: Kill off s_options and helpers
2017-07-11 06:09:21 -04:00
efs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
exofs
Merge branch 'for-4.14/block' of git://git.kernel.dk/linux-block
2017-09-07 11:59:42 -07:00
exportfs
…
ext2
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
ext4
ext4: fix crash when a directory's i_size is too small
2017-12-20 10:10:22 +01:00
f2fs
f2fs: fix to clear FI_NO_PREALLOC
2017-12-14 09:53:14 +01:00
fat
fs/fat/inode.c: fix sb_rdonly() change
2017-12-05 11:26:29 +01:00
freevxfs
…
fscache
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
fuse
fuse: fix READDIRPLUS skipping an entry
2017-10-25 16:34:27 +02:00
gfs2
GFS2: Take inode off order_write list when setting jdata flag
2017-12-20 10:10:29 +01:00
hfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
hfsplus
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
hostfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
hpfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
hugetlbfs
fs/hugetlbfs/inode.c: fix hwpoison reserve accounting
2017-11-03 07:39:19 -07:00
isofs
isofs: fix timestamps beyond 2027
2017-11-30 08:40:45 +00:00
jbd2
Writeback error handling fixes (pile #2)
2017-07-07 19:38:17 -07:00
jffs2
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
jfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
kernfs
Merge branch 'for-4.14/block' of git://git.kernel.dk/linux-block
2017-09-07 11:59:42 -07:00
lockd
lockd: lost rollback of set_grace_period() in lockd_down_net()
2017-12-05 11:26:30 +01:00
minix
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
ncpfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
nfs
nfs: don't wait on commit in nfs_commit_inode() if there were no commit requests
2017-12-20 10:10:20 +01:00
nfs_common
…
nfsd
kernel: make groups_sort calling a responsibility group_info allocators
2017-12-20 10:10:18 +01:00
nilfs2
nilfs2: fix race condition that causes file system corruption
2017-11-30 08:40:44 +00:00
nls
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
notify
fsnotify: fix pinning group in fsnotify_prepare_user_wait()
2017-11-30 08:40:47 +00:00
ntfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
ocfs2
ocfs2: should wait dio before inode lock in ocfs2_setattr()
2017-11-24 08:37:04 +01:00
omfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
openpromfs
…
orangefs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
overlayfs
locking/barriers: Convert users of lockless_dereference() to READ_ONCE()
2017-12-25 14:26:21 +01:00
proc
proc: fix coredump vs read /proc/*/stat race
2018-01-23 19:58:18 +01:00
pstore
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
qnx4
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
qnx6
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
quota
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
ramfs
mm: make pagevec_lookup() update index
2017-09-06 17:27:26 -07:00
reiserfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
romfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
squashfs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
sysfs
…
sysv
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
tracefs
VFS: Don't use save/replace_mount_options if not using generic_show_options
2017-07-06 03:31:46 -04:00
ubifs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
udf
udf: Avoid overflow when session starts at large offset
2017-12-20 10:10:36 +01:00
ufs
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
xfs
xfs: fix incorrect extent state in xfs_bmap_add_extent_unwritten_real
2017-12-20 10:10:32 +01:00
aio.c
Merge branch 'work.read_write' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2017-09-14 19:29:55 -07:00
anon_inodes.c
…
attr.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
bad_inode.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
binfmt_aout.c
fs: fix kernel_read prototype
2017-09-04 19:05:15 -04:00
binfmt_elf_fdpic.c
Merge branch 'work.set_fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2017-09-14 18:13:32 -07:00
binfmt_elf.c
Merge branch 'work.set_fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2017-09-14 18:13:32 -07:00
binfmt_em86.c
…
binfmt_flat.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
binfmt_misc.c
fs/binfmt_misc.c: node could be NULL when evicting inode
2017-10-13 16:18:33 -07:00
binfmt_script.c
exec: load_script: kill the onstack interp[BINPRM_BUF_SIZE] array
2017-10-03 17:54:25 -07:00
block_dev.c
fs/mpage.c: fix mpage_writepage() for pages with buffers
2017-10-13 16:18:33 -07:00
buffer.c
fs: guard_bio_eod() needs to consider partitions
2017-11-30 08:40:45 +00:00
char_dev.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
compat_binfmt_elf.c
…
compat_ioctl.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
compat.c
…
coredump.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
dax.c
dax: fix PMD faults on zero-length files
2017-11-30 08:40:53 +00:00
dcache.c
locking/barriers: Convert users of lockless_dereference() to READ_ONCE()
2017-12-25 14:26:21 +01:00
dcookies.c
…
direct-io.c
Changes since last update:
2017-10-18 14:51:50 -04:00
drop_caches.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
eventfd.c
…
eventpoll.c
fs/epoll: use faster rb_first_cached()
2017-09-08 18:26:49 -07:00
exec.c
exec: Weaken dumpability for secureexec
2018-01-05 15:48:57 +01:00
fcntl.c
fcntl: don't cap l_start and l_end values for F_GETLK64 in compat syscall
2017-12-17 15:07:59 +01:00
fhandle.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
file_table.c
fput: Don't reinvent the wheel but use existing llist API
2017-08-28 00:50:23 -04:00
file.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
filesystems.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
fs_pin.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
fs_struct.c
…
fs-writeback.c
writeback: rework wb_[dec|inc]_stat family of functions
2017-07-12 16:26:05 -07:00
inode.c
Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
2017-09-13 09:11:44 -07:00
internal.h
Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
2017-09-13 09:11:44 -07:00
ioctl.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
iomap.c
fs: invalidate page cache after end_io() in dio completion
2017-10-16 12:11:56 -07:00
Kconfig
fs/Kconfig: kill CONFIG_PERCPU_RWSEM some more
2017-07-12 16:26:00 -07:00
Kconfig.binfmt
…
libfs.c
fs: convert __generic_file_fsync to use errseq_t based reporting
2017-07-06 07:02:29 -04:00
locks.c
locks: restore a warn for leaked locks on close
2017-07-21 13:57:31 -04:00
Makefile
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
mbcache.c
…
mount.h
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
mpage.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
namei.c
autofs: revert "autofs: fix AT_NO_AUTOMOUNT not being honored"
2017-12-05 11:26:29 +01:00
namespace.c
vfs: fix mounting a filesystem with i_version
2017-10-17 02:22:07 -04:00
no-block.c
…
nsfs.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
open.c
ovl: don't allow writing ioctl on lower layer
2017-09-05 12:53:12 +02:00
pipe.c
pipe: avoid round_pipe_size() nr_pages overflow on 32-bit
2018-01-23 19:58:14 +01:00
pnode.c
…
pnode.h
…
posix_acl.c
…
proc_namespace.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
read_write.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
readdir.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
select.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
seq_file.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
signalfd.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
splice.c
fs: move kernel_write to fs/read_write.c
2017-09-04 19:05:15 -04:00
stack.c
…
stat.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
statfs.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
super.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
sync.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
timerfd.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
userfaultfd.c
userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails
2018-01-10 09:31:17 +01:00
utimes.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
xattr.c
lsm: fix smack_inode_removexattr and xattr_getsecurity memleak
2017-10-04 18:03:15 +11:00