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Eddie.Horng 5a842ecca2 cap_inode_getsecurity: use d_find_any_alias() instead of d_find_alias() 
commit 355139a8db upstream.

The code in cap_inode_getsecurity(), introduced by commit 8db6c34f1d
("Introduce v3 namespaced file capabilities"), should use
d_find_any_alias() instead of d_find_alias() do handle unhashed dentry
correctly. This is needed, for example, if execveat() is called with an
open but unlinked overlayfs file, because overlayfs unhashes dentry on
unlink.
This is a regression of real life application, first reported at
https://www.spinics.net/lists/linux-unionfs/msg05363.html

Below reproducer and setup can reproduce the case.
  const char* exec="echo";
  const char *newargv[] = { "echo", "hello", NULL};
  const char *newenviron[] = { NULL };
  int fd, err;

  fd = open(exec, O_PATH);
  unlink(exec);
  err = syscall(322/*SYS_execveat*/, fd, "", newargv, newenviron,
AT_EMPTY_PATH);
  if(err<0)
    fprintf(stderr, "execveat: %s\n", strerror(errno));

gcc compile into ~/test/a.out
mount -t overlay -orw,lowerdir=/mnt/l,upperdir=/mnt/u,workdir=/mnt/w
none /mnt/m
cd /mnt/m
cp /bin/echo .
~/test/a.out

Expected result:
hello
Actually result:
execveat: Invalid argument
dmesg:
Invalid argument reading file caps for /dev/fd/3

The 2nd reproducer and setup emulates similar case but for
regular filesystem:
  const char* exec="echo";
  int fd, err;
  char buf[256];

  fd = open(exec, O_RDONLY);
  unlink(exec);
  err = fgetxattr(fd, "security.capability", buf, 256);
  if(err<0)
    fprintf(stderr, "fgetxattr: %s\n", strerror(errno));

gcc compile into ~/test_fgetxattr

cd /tmp
cp /bin/echo .
~/test_fgetxattr

Result:
fgetxattr: Invalid argument

On regular filesystem, for example, ext4 read xattr from
disk and return to execveat(), will not trigger this issue, however,
the overlay attr handler pass real dentry to vfs_getxattr() will.
This reproducer calls fgetxattr() with an unlinked fd, involkes
vfs_getxattr() then reproduced the case that d_find_alias() in
cap_inode_getsecurity() can't find the unlinked dentry.

Suggested-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Fixes: 8db6c34f1d ("Introduce v3 namespaced file capabilities")
Cc: <stable@vger.kernel.org> # v4.14
Signed-off-by: Eddie Horng <eddie.horng@mediatek.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2018-09-09 19:56:01 +02:00
Documentation kbuild: verify that $DEPMOD is installed 2018-08-17 21:01:10 +02:00
arch sys: don't hold uts_sem while accessing userspace memory 2018-09-09 19:56:00 +02:00
block block, bfq: return nbytes and not zero from struct cftype .write() method 2018-09-09 19:55:59 +02:00
certs Replace magic for trusting the secondary keyring with #define 2018-09-09 19:55:54 +02:00
crypto Replace magic for trusting the secondary keyring with #define 2018-09-09 19:55:54 +02:00
drivers bcache: release dc->writeback_lock properly in bch_writeback_thread() 2018-09-09 19:56:01 +02:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs getxattr: use correct xattr length 2018-09-09 19:56:01 +02:00
include udlfb: set optimal write delay 2018-09-09 19:56:01 +02:00
init init: rename and re-order boot_cpu_state_init() 2018-08-15 18:12:48 +02:00
ipc ipc/sem.c: prevent queue.status tearing in semop 2018-09-05 09:26:30 +02:00
kernel userns: move user access out of the mutex 2018-09-09 19:56:00 +02:00
lib printk/nmi: Prevent deadlock when accessing the main log buffer in NMI 2018-09-05 09:26:35 +02:00
mm mm/tlb: Remove tlb_remove_table() non-concurrent condition 2018-09-09 19:55:59 +02:00
net NFSv4 client live hangs after live data migration recovery 2018-09-09 19:55:59 +02:00
samples samples/bpf: Check the error of write() and read() 2018-08-24 13:09:12 +02:00
scripts gcc-plugins: Use dynamic initializers 2018-09-05 09:26:42 +02:00
security cap_inode_getsecurity: use d_find_any_alias() instead of d_find_alias() 2018-09-09 19:56:01 +02:00
sound ASoC: sirf: Fix potential NULL pointer dereference 2018-09-05 09:26:39 +02:00
tools tools/power turbostat: Read extended processor family from CPUID 2018-09-05 09:26:30 +02:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: Skip updating PTE entry if no change 2018-09-05 09:26:36 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
…
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS dt-bindings: Document mti,mips-cpc binding 2018-03-15 10:54:35 +01:00
Makefile Linux 4.14.68 2018-09-05 09:26:42 +02:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.