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Eric W. Biederman f928ef685d ucounts: Silence warning in dec_rlimit_ucounts
Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> url:    https://github.com/0day-ci/linux/commits/legion-kernel-org/Count-rlimits-in-each-user-namespace/20210427-162857
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git next
> config: arc-randconfig-m031-20210426 (attached as .config)
> compiler: arceb-elf-gcc (GCC) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> smatch warnings:
> kernel/ucount.c:270 dec_rlimit_ucounts() error: uninitialized symbol 'new'.
>
> vim +/new +270 kernel/ucount.c
>
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  260  bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v)
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  261  {
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  262   struct ucounts *iter;
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  263   long new;
>                                                 ^^^^^^^^
>
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  264   for (iter = ucounts; iter; iter = iter->ns->ucounts) {
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  265    long dec = atomic_long_add_return(-v, &iter->ucount[type]);
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  266    WARN_ON_ONCE(dec < 0);
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  267    if (iter == ucounts)
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  268     new = dec;
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  269   }
> 176ec2b092cc22 Alexey Gladkov 2021-04-22 @270   return (new == 0);
>                                                         ^^^^^^^^
> I don't know if this is a bug or not, but I can definitely tell why the
> static checker complains about it.
>
> 176ec2b092cc22 Alexey Gladkov 2021-04-22  271  }

In the only two cases that care about the return value of
dec_rlimit_ucounts the code first tests to see that ucounts is not
NULL.  In those cases it is guaranteed at least one iteration of the
loop will execute guaranteeing the variable new will be initialized.

Initialize new to -1 so that the return value is well defined even
when the loop does not execute and the static checker is silenced.

Link: https://lkml.kernel.org/r/m1tunny77w.fsf@fess.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-04-30 14:25:40 -05:00
arch - Fix BDW Xeon's stepping in the PEBS isolation table of CPUs 2021-04-25 09:42:06 -07:00
block block: return -EBUSY when there are open partitions in blkdev_reread_part 2021-04-21 10:49:37 -06:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto crypto: mips/poly1305 - enable for all MIPS processors 2021-03-08 11:52:17 +01:00
Documentation Networking fixes for 5.12-rc8, including fixes from netfilter, 2021-04-17 09:57:15 -07:00
drivers Late pin control fixes for v5.12: 2021-04-23 17:11:10 -07:00
fs Reimplement RLIMIT_MEMLOCK on top of ucounts 2021-04-30 14:14:02 -05:00
include ucounts: Set ucount_max to the largest positive value the type can hold 2021-04-30 14:14:03 -05:00
init Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
ipc Reimplement RLIMIT_MEMLOCK on top of ucounts 2021-04-30 14:14:02 -05:00
kernel ucounts: Silence warning in dec_rlimit_ucounts 2021-04-30 14:25:40 -05:00
lib lib: remove "expecting prototype" kernel-doc warnings 2021-04-16 16:10:37 -07:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm Reimplement RLIMIT_MEMLOCK on top of ucounts 2021-04-30 14:14:02 -05:00
net Revert "net/rds: Avoid potential use after free in rds_send_remove_from_sock" 2021-04-24 09:32:35 -07:00
samples Merge git://git.kernel.org:/pub/scm/linux/kernel/git/netdev/net 2021-03-09 17:15:56 -08:00
scripts kasan: remove redundant config option 2021-04-16 16:10:36 -07:00
security KEYS: trusted: Fix TPM reservation for seal/unseal 2021-04-21 16:28:20 -07:00
sound sound fixes for 5.12-rc7 2021-04-08 09:01:30 -07:00
tools kselftests: Add test to check for rlimit changes in different user namespaces 2021-04-30 14:14:03 -05:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.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 clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap .mailmap: fix old email addresses 2021-04-09 14:54:23 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
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 ARM SoC fixes for v5.12, part 2 2021-04-18 13:23:26 -07:00
Makefile Linux 5.12 2021-04-25 13:49:08 -07:00
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.