Re: [PATCH v3] sysctl: expose sysctl_check_table for unit testing and use it

[Joel Granados]

On Sun, Jan 12, 2025 at 11:00:01PM -0800, John Sperbeck wrote:
> In commit b5ffbd139688 ("sysctl: move the extra1/2 boundary check
> of u8 to sysctl_check_table_array"), a kunit test was added that
> registers a sysctl table.  If the test is run as a module, then a
> lingering reference to the module is left behind, and a 'sysctl -a'
> leads to a panic.
> 
> This can be reproduced with these kernel config settings:
> 
>     CONFIG_KUNIT=y
>     CONFIG_SYSCTL_KUNIT_TEST=m
> 
> Then run these commands:
> 
>     modprobe sysctl-test
>     rmmod sysctl-test
>     sysctl -a
> 
> The panic varies but generally looks something like this:
> 
>     BUG: unable to handle page fault for address: ffffa4571c0c7db4
>     #PF: supervisor read access in kernel mode
>     #PF: error_code(0x0000) - not-present page
>     PGD 100000067 P4D 100000067 PUD 100351067 PMD 114f5e067 PTE 0
>     Oops: Oops: 0000 [#1] SMP NOPTI
>     ... ... ...
>     RIP: 0010:proc_sys_readdir+0x166/0x2c0
>     ... ... ...
>     Call Trace:
>      <TASK>
>      iterate_dir+0x6e/0x140
>      __se_sys_getdents+0x6e/0x100
>      do_syscall_64+0x70/0x150
>      entry_SYSCALL_64_after_hwframe+0x76/0x7e
> 
> Instead of fully registering a sysctl table, expose the underlying
> checking function and use it in the unit test.
> 
> Fixes: b5ffbd139688 ("sysctl: move the extra1/2 boundary check of u8 to sysctl_check_table_array")
> Signed-off-by: John Sperbeck <jsperbeck@xxxxxxxxxx>
You have received a error from the bot. please address it to move
forward.

Best
> ---
>  fs/proc/proc_sysctl.c  | 22 +++++++++++++++++-----
>  include/linux/sysctl.h |  8 ++++++++
>  kernel/sysctl-test.c   |  9 ++++++---
>  3 files changed, 31 insertions(+), 8 deletions(-)
> 
...
>  
>  static struct kunit_case sysctl_test_cases[] = {
> -- 
> 2.47.1.613.gc27f4b7a9f-goog
> 

-- 

Joel Granados