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Fix -Wstringop-overflow warnings in kernel/cgroup/cgroup.c #316

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GustavoARSilva opened this issue Jun 15, 2023 · 2 comments
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Fix -Wstringop-overflow warnings in kernel/cgroup/cgroup.c #316

GustavoARSilva opened this issue Jun 15, 2023 · 2 comments
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-Wstringop-overflow Emits warnings under -Wstringop-overflow [PATCH] Exists A patch exists to address the issue

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Found in ARM aspeed_g4_defconfig

kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
@GustavoARSilva GustavoARSilva added the -Wstringop-overflow Emits warnings under -Wstringop-overflow label Jun 15, 2023
@GustavoARSilva GustavoARSilva self-assigned this Jun 15, 2023
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Patch: https://lore.kernel.org/linux-hardening/ZIpm3pcs3iCP9UaR@work/

@GustavoARSilva GustavoARSilva mentioned this issue Jun 16, 2023
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@GustavoARSilva GustavoARSilva added the [PATCH] Exists A patch exists to address the issue label Jun 20, 2023
intel-lab-lkp pushed a commit to intel-lab-lkp/linux that referenced this issue Aug 16, 2023
@GustavoARSilva @intel-lab-lkp
cgroup: Avoid -Wstringop-overflow warnings
6b2fc86 
Change the notation from pointer-to-array to pointer-to-pointer.
With this, we avoid the compiler complaining about trying
to access a region of size zero as an argument during function
calls.

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):

kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

This results in no differences in binary output.

Link: KSPP#316
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
intel-lab-lkp pushed a commit to intel-lab-lkp/linux that referenced this issue Aug 17, 2023
@GustavoARSilva @intel-lab-lkp
cgroup: Avoid -Wstringop-overflow warnings
62b495a 
Change the notation from pointer-to-array to pointer-to-pointer.
With this, we avoid the compiler complaining about trying
to access a region of size zero as an argument during function
calls.

This is a workaround to prevent the compiler complaining about
accessing an array of size zero when evaluating the arguments
of a couple of function calls. See below:

kernel/cgroup/cgroup.c: In function 'find_css_set':
kernel/cgroup/cgroup.c:1206:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
 1206 |         cset = find_existing_css_set(old_cset, cgrp, template);
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/cgroup/cgroup.c:1206:16: note: referencing argument 3 of type 'struct cgroup_subsys_state *[0]'
kernel/cgroup/cgroup.c:1071:24: note: in a call to function 'find_existing_css_set'
 1071 | static struct css_set *find_existing_css_set(struct css_set *old_cset,
      |                        ^~~~~~~~~~~~~~~~~~~~~

With the change to pointer-to-pointer, the functions are not prevented
from being executed, and they will do what they have to do when
CGROUP_SUBSYS_COUNT == 0.

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):

kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

This results in no differences in binary output.

Link: KSPP#316
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
@GustavoARSilva
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fixed in commit 78d44b8

bella485 pushed a commit to bella485/centos-stream-9 that referenced this issue May 1, 2024
cgroup: Avoid -Wstringop-overflow warnings
8ee0342 
JIRA: https://issues.redhat.com/browse/RHEL-34600

commit 78d44b824ed04dd1553c55c5b839c9a55cbcaf4e
Author: Gustavo A. R. Silva <gustavoars@kernel.org>
Date:   Thu, 17 Aug 2023 11:19:13 -0600

    cgroup: Avoid -Wstringop-overflow warnings

    Change the notation from pointer-to-array to pointer-to-pointer.
    With this, we avoid the compiler complaining about trying
    to access a region of size zero as an argument during function
    calls.

    This is a workaround to prevent the compiler complaining about
    accessing an array of size zero when evaluating the arguments
    of a couple of function calls. See below:

    kernel/cgroup/cgroup.c: In function 'find_css_set':
    kernel/cgroup/cgroup.c:1206:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
     1206 |         cset = find_existing_css_set(old_cset, cgrp, template);
          |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    kernel/cgroup/cgroup.c:1206:16: note: referencing argument 3 of type 'struct cgroup_subsys_state *[0]'
    kernel/cgroup/cgroup.c:1071:24: note: in a call to function 'find_existing_css_set'
     1071 | static struct css_set *find_existing_css_set(struct css_set *old_cset,
          |                        ^~~~~~~~~~~~~~~~~~~~~

    With the change to pointer-to-pointer, the functions are not prevented
    from being executed, and they will do what they have to do when
    CGROUP_SUBSYS_COUNT == 0.

    Address the following -Wstringop-overflow warnings seen when
    built with ARM architecture and aspeed_g4_defconfig configuration
    (notice that under this configuration CGROUP_SUBSYS_COUNT == 0):

    kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
    kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
    kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]
    kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

    This results in no differences in binary output.

    Link: KSPP/linux#316
    Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
    Reviewed-by: Kees Cook <keescook@chromium.org>
    Signed-off-by: Tejun Heo <tj@kernel.org>

Signed-off-by: Waiman Long <longman@redhat.com>
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