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>
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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
