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Cengiz Can 1db11e71cf blktrace: fix dereference after null check
[ Upstream commit 153031a301 ]

There was a recent change in blktrace.c that added a RCU protection to
`q->blk_trace` in order to fix a use-after-free issue during access.

However the change missed an edge case that can lead to dereferencing of
`bt` pointer even when it's NULL:

Coverity static analyzer marked this as a FORWARD_NULL issue with CID
1460458.

```
/kernel/trace/blktrace.c: 1904 in sysfs_blk_trace_attr_store()
1898            ret = 0;
1899            if (bt == NULL)
1900                    ret = blk_trace_setup_queue(q, bdev);
1901
1902            if (ret == 0) {
1903                    if (attr == &dev_attr_act_mask)
>>>     CID 1460458:  Null pointer dereferences  (FORWARD_NULL)
>>>     Dereferencing null pointer "bt".
1904                            bt->act_mask = value;
1905                    else if (attr == &dev_attr_pid)
1906                            bt->pid = value;
1907                    else if (attr == &dev_attr_start_lba)
1908                            bt->start_lba = value;
1909                    else if (attr == &dev_attr_end_lba)
```

Added a reassignment with RCU annotation to fix the issue.

Fixes: c780e86dd4 ("blktrace: Protect q->blk_trace with RCU")
Cc: stable@vger.kernel.org
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Cengiz Can <cengiz@kernel.wtf>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2020-03-12 07:18:23 +01:00
arch kvm: nVMX: VMWRITE checks unsupported field before read-only field 2020-03-05 16:45:25 +01:00
block block, bfq: do not insert oom queue into position tree 2020-03-12 07:18:22 +01:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto crypto: rename sm3-256 to sm3 in hash_algo_name 2020-02-28 17:23:43 +01:00
Documentation netfilter: nf_flowtable: fix documentation 2020-03-05 16:45:24 +01:00
drivers RDMA/core: Fix use of logical OR in get_new_pps 2020-03-12 07:18:23 +01:00
fs xfs: clear kernel only flags in XFS_IOC_ATTRMULTI_BY_HANDLE 2020-03-05 16:45:25 +01:00
include lib/vdso: Make __arch_update_vdso_data() logic understandable 2020-03-05 16:45:22 +01:00
init Revert "um: Enable CONFIG_CONSTRUCTORS" 2020-02-01 09:33:00 +00:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-28 17:23:36 +01:00
kernel blktrace: fix dereference after null check 2020-03-12 07:18:23 +01:00
lib crypto: chacha20poly1305 - prevent integer overflow on large input 2020-02-28 17:23:40 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm, thp: fix defrag setting if newline is not used 2020-03-05 16:45:25 +01:00
net netfilter: nft_tunnel: no need to call htons() when dumping ports 2020-03-05 16:45:24 +01:00
samples samples/bpf: Set -fno-stack-protector when building BPF programs 2020-02-24 08:38:15 +01:00
scripts kbuild: fix DT binding schema rule to detect command line changes 2020-03-05 16:45:19 +01:00
security ima: ima/lsm policy rule loading logic bug fixes 2020-03-05 16:45:22 +01:00
sound ASoC: intel/skl/hda - export number of digital microphones via control components 2020-03-12 07:18:22 +01:00
tools perf maps: Add missing unlock to maps__insert() error case 2020-03-05 16:45:23 +01:00
usr gen_initramfs_list.sh: fix 'bad variable name' error 2020-01-04 00:00:48 +09:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-05 16:45:21 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +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 modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap MAINTAINERS: update my email address 2020-01-11 14:33:39 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Linux 5.4-rc4 2019-10-29 04:43:29 -06:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 17:23:36 +01:00
Makefile Linux 5.5.8 2020-03-05 16:45:26 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.