Commit graph

4 commits

Author SHA1 Message Date
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
Al Viro
f2683bd8d5 [PATCH] fix d_absolute_path() interplay with fsmount()
stuff in anon namespace should be treated as unattached.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-08-30 19:31:09 -04:00
Al Viro
7e5f7bb08b unexport simple_dname()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-05-21 08:23:41 +01:00
Al Viro
7a5cf791a7 split d_path() and friends into a separate file
Those parts of fs/dcache.c are pretty much self-contained.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:46 -04:00