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Carlos Llamas 43bed0a13a mm/mmap: undo ->mmap() when arch_validate_flags() fails 
commit deb0f65628 upstream.

Commit c462ac288f ("mm: Introduce arch_validate_flags()") added a late
check in mmap_region() to let architectures validate vm_flags.  The check
needs to happen after calling ->mmap() as the flags can potentially be
modified during this callback.

If arch_validate_flags() check fails we unmap and free the vma.  However,
the error path fails to undo the ->mmap() call that previously succeeded
and depending on the specific ->mmap() implementation this translates to
reference increments, memory allocations and other operations what will
not be cleaned up.

There are several places (mainly device drivers) where this is an issue.
However, one specific example is bpf_map_mmap() which keeps count of the
mappings in map->writecnt.  The count is incremented on ->mmap() and then
decremented on vm_ops->close().  When arch_validate_flags() fails this
count is off since bpf_map_mmap_close() is never called.

One can reproduce this issue in arm64 devices with MTE support.  Here the
vm_flags are checked to only allow VM_MTE if VM_MTE_ALLOWED has been set
previously.  From userspace then is enough to pass the PROT_MTE flag to
mmap() syscall to trigger the arch_validate_flags() failure.

The following program reproduces this issue:

  #include <stdio.h>
  #include <unistd.h>
  #include <linux/unistd.h>
  #include <linux/bpf.h>
  #include <sys/mman.h>

  int main(void)
  {
	union bpf_attr attr = {
		.map_type = BPF_MAP_TYPE_ARRAY,
		.key_size = sizeof(int),
		.value_size = sizeof(long long),
		.max_entries = 256,
		.map_flags = BPF_F_MMAPABLE,
	};
	int fd;

	fd = syscall(__NR_bpf, BPF_MAP_CREATE, &attr, sizeof(attr));
	mmap(NULL, 4096, PROT_WRITE | PROT_MTE, MAP_SHARED, fd, 0);

	return 0;
  }

By manually adding some log statements to the vm_ops callbacks we can
confirm that when passing PROT_MTE to mmap() the map->writecnt is off upon
->release():

With PROT_MTE flag:
  root@debian:~# ./bpf-test
  [  111.263874] bpf_map_write_active_inc: map=9 writecnt=1
  [  111.288763] bpf_map_release: map=9 writecnt=1

Without PROT_MTE flag:
  root@debian:~# ./bpf-test
  [  157.816912] bpf_map_write_active_inc: map=10 writecnt=1
  [  157.830442] bpf_map_write_active_dec: map=10 writecnt=0
  [  157.832396] bpf_map_release: map=10 writecnt=0

This patch fixes the above issue by calling vm_ops->close() when the
arch_validate_flags() check fails, after this we can proceed to unmap and
free the vma on the error path.

Link: https://lkml.kernel.org/r/20220930003844.1210987-1-cmllamas@google.com
Fixes: c462ac288f ("mm: Introduce arch_validate_flags()")
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Liam Howlett <liam.howlett@oracle.com>
Cc: Christian Brauner (Microsoft) <brauner@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>	[5.10+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-10-26 12:34:24 +02:00
arch arm64: errata: Add Cortex-A55 to the repeat tlbi list 2022-10-26 12:34:24 +02:00
block block: blk_queue_enter() / __bio_queue_enter() must return -EAGAIN for nowait 2022-09-23 14:15:48 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto KEYS: asymmetric: enforce SM2 signature use pkey algo 2022-08-17 14:24:28 +02:00
Documentation arm64: errata: Add Cortex-A55 to the repeat tlbi list 2022-10-26 12:34:24 +02:00
drivers drm/udl: Restore display mode on resume 2022-10-26 12:34:24 +02:00
fs quota: Check next/prev free block number after reading from quota file 2022-10-26 12:34:21 +02:00
include scsi: stex: Properly zero out the passthrough command structure 2022-10-15 07:59:01 +02:00
init stack: Declare {randomize_,}kstack_offset to fix Sparse warnings 2022-08-17 14:23:10 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:23:10 +02:00
kernel swiotlb: max mapping size takes min align mask into account 2022-10-05 10:39:40 +02:00
lib crypto: lib - remove unneeded selection of XOR_BLOCKS 2022-09-05 10:30:03 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/mmap: undo ->mmap() when arch_validate_flags() fails 2022-10-26 12:34:24 +02:00
net wifi: mac80211: fix MBSSID parsing use-after-free 2022-10-15 07:59:05 +02:00
samples samples/landlock: Format with clang-format 2022-06-09 10:23:23 +02:00
scripts Makefile.extrawarn: Move -Wcast-function-type-strict to W=1 2022-10-12 09:53:26 +02:00
security efi: Correct Macmini DMI match in uefi cert quirk 2022-10-15 07:59:01 +02:00
sound ASoC: wcd934x: fix order of Slimbus unprepare/disable 2022-10-26 12:34:21 +02:00
tools perf parse-events: Identify broken modifiers 2022-10-12 09:53:28 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: SEV: add cache flush to solve SEV cache incoherency issues 2022-09-23 14:15:52 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.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: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 Input: goodix - add a goodix.h header file 2022-07-12 16:34:51 +02:00
Makefile Linux 5.15.74 2022-10-15 07:59:05 +02:00
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.