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Andrii Nakryiko 09cad07547 fs: fix NULL dereference due to data race in prepend_path()
Fix data race in prepend_path() with re-reading mnt->mnt_ns twice
without holding the lock.

is_mounted() does check for NULL, but is_anon_ns(mnt->mnt_ns) might
re-read the pointer again which could be NULL already, if in between
reads one of kern_unmount()/kern_unmount_array()/umount_tree() sets
mnt->mnt_ns to NULL.

This is seen in production with the following stack trace:

  BUG: kernel NULL pointer dereference, address: 0000000000000048
  ...
  RIP: 0010:prepend_path.isra.4+0x1ce/0x2e0
  Call Trace:
    d_path+0xe6/0x150
    proc_pid_readlink+0x8f/0x100
    vfs_readlink+0xf8/0x110
    do_readlinkat+0xfd/0x120
    __x64_sys_readlinkat+0x1a/0x20
    do_syscall_64+0x42/0x110
    entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: f2683bd8d5 ("[PATCH] fix d_absolute_path() interplay with fsmount()")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-14 14:54:45 -07:00
Documentation kernel-clone-v5.9 2020-10-14 14:32:52 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch kernel-clone-v5.9 2020-10-14 14:32:52 -07:00
block drivers-5.10-2020-10-12 2020-10-13 13:04:41 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto drivers-5.10-2020-10-12 2020-10-13 13:04:41 -07:00
drivers kernel-clone-v5.9 2020-10-14 14:32:52 -07:00
fs fs: fix NULL dereference due to data race in prepend_path() 2020-10-14 14:54:45 -07:00
include threads-v5.10 2020-10-14 14:39:20 -07:00
init printk changes for 5.10 2020-10-13 15:58:10 -07:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel threads-v5.10 2020-10-14 14:39:20 -07:00
lib mm/page_alloc.c: fix freeing non-compound pages 2020-10-13 18:38:33 -07:00
mm mm/migrate: remove obsolete comment about device public 2020-10-13 18:38:36 -07:00
net io_uring-5.10-2020-10-12 2020-10-13 12:36:21 -07:00
samples kernel-clone-v5.9 2020-10-14 14:32:52 -07:00
scripts Merge branch 'akpm' (patches from Andrew) 2020-10-14 09:57:24 -07:00
security selinux/stable-5.10 PR 20201012 2020-10-13 16:29:55 -07:00
sound sound fixes for 5.9-rc7 2020-09-24 09:00:05 -07:00
tools threads-v5.10 2020-10-14 14:39:20 -07:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: fix memory leak in kvm_io_bus_unregister_dev() 2020-09-11 13:15:11 -04:00
.clang-format memblock: use separate iterators for memory and reserved regions 2020-10-13 18:38:35 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap As hoped, things calmed down for docs this cycle; fewer changes and almost 2020-10-12 16:21:29 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS IOMMU Updates for Linux v5.10 2020-10-14 12:08:34 -07:00
Makefile Revert "kbuild: disable clang's default use of -fmerge-all-constants" 2020-10-13 18:38:26 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.