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Nico Boehr f219ea71ee KVM: s390: fix KVM_S390_GET_CMMA_BITS for GFNs in memslot holes 
[ Upstream commit 285cff4c04 ]

The KVM_S390_GET_CMMA_BITS ioctl may return incorrect values when userspace
specifies a start_gfn outside of memslots.

This can occur when a VM has multiple memslots with a hole in between:

+-----+----------+--------+--------+
| ... | Slot N-1 | <hole> | Slot N |
+-----+----------+--------+--------+
      ^          ^        ^        ^
      |          |        |        |
GFN   A          A+B      |        |
                          A+B+C    |
			           A+B+C+D

When userspace specifies a GFN in [A+B, A+B+C), it would expect to get the
CMMA values of the first dirty page in Slot N. However, userspace may get a
start_gfn of A+B+C+D with a count of 0, hence completely skipping over any
dirty pages in slot N.

The error is in kvm_s390_next_dirty_cmma(), which assumes
gfn_to_memslot_approx() will return the memslot _below_ the specified GFN
when the specified GFN lies outside a memslot. In reality it may return
either the memslot below or above the specified GFN.

When a memslot above the specified GFN is returned this happens:

- ofs is calculated, but since the memslot's base_gfn is larger than the
  specified cur_gfn, ofs will underflow to a huge number.
- ofs is passed to find_next_bit(). Since ofs will exceed the memslot's
  number of pages, the number of pages in the memslot is returned,
  completely skipping over all bits in the memslot userspace would be
  interested in.

Fix this by resetting ofs to zero when a memslot _above_ cur_gfn is
returned (cur_gfn < ms->base_gfn).

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Fixes: afdad61615 ("KVM: s390: Fix storage attributes migration with memory slots")
Message-Id: <20230324145424.293889-2-nrb@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-07-23 13:47:24 +02:00
arch KVM: s390: fix KVM_S390_GET_CMMA_BITS for GFNs in memslot holes 2023-07-23 13:47:24 +02:00
block block: increment diskseq on all media change events 2023-07-23 13:47:20 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto KEYS: asymmetric: Copy sig and digest in public_key_verify_signature() 2023-06-09 10:32:34 +02:00
Documentation Remove DECnet support from kernel 2023-06-21 15:59:15 +02:00
drivers media: atomisp: gmin_platform: fix out_len in gmin_get_config_dsm_var() 2023-07-23 13:47:24 +02:00
fs kernfs: fix missing kernfs_idr_lock to remove an ID from the IDR 2023-07-23 13:47:23 +02:00
include media: videodev2.h: Fix struct v4l2_input tuner index comment 2023-07-23 13:47:21 +02:00
init kbuild: Add CONFIG_PAHOLE_VERSION 2023-02-25 12:06:45 +01:00
io_uring io_uring: ensure IOPOLL locks around deferred work 2023-07-23 13:47:18 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel kcsan: Don't expect 64 bits atomic builtins from 32 bits architectures 2023-07-23 13:47:12 +02:00
lib lib/ts_bm: reset initial match offset for every block of text 2023-07-23 13:46:56 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm, hwpoison: when copy-on-write hits poison, take page offline 2023-07-05 18:25:04 +01:00
net SUNRPC: Fix UAF in svc_tcp_listen_data_ready() 2023-07-23 13:47:20 +02:00
samples samples/bpf: Fix buffer overflow in tcp_basertt 2023-07-23 13:46:49 +02:00
scripts kbuild: Disable GCOV for *.mod.o 2023-07-23 13:47:17 +02:00
security ima: Fix build warnings 2023-07-23 13:46:48 +02:00
sound ALSA: jack: Fix mutex call in snd_jack_report() 2023-07-23 13:47:19 +02:00
tools perf dwarf-aux: Fix off-by-one in die_get_varname() 2023-07-23 13:47:12 +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: Avoid illegal stage2 mapping on invalid memory slot 2023-06-28 10:29:42 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 Remove DECnet support from kernel 2023-06-21 15:59:15 +02:00
Makefile Linux 5.15.120 2023-07-05 18:25:05 +01:00
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.