Sysctl handlers are not supposed to modify the ctl_table passed to them. Adapt the logic to work with a temporary variable, similar to how it is done in other parts of the kernel.
This is also a prerequisite to enforce the immutability of the argument through the callbacks prototy.
Fixes: 964c9dff0091 ("stackleak: Allow runtime disabling of kernel stack erasing") Cc: stable@vger.kernel.org Acked-by: Kees Cook keescook@chromium.org Reviewed-by: Luis Chamberlain mcgrof@kernel.org Signed-off-by: Thomas Weißschuh linux@weissschuh.net --- This was split out of my sysctl-const-handler series [0].
As that series will take some more time, submit the patch on its own, as it is a generic bugfix that is valuable on its own. And I can get it out of my books.
Changelog in contrast to the patch in the series: * Reword commit message to remove strong relation to the constification * Cc stable
[0] https://lore.kernel.org/lkml/20240423-sysctl-const-handler-v3-0-e0beccb836e2...
Cc: Joel Granados j.granados@samsung.com --- kernel/stackleak.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/stackleak.c b/kernel/stackleak.c index 34c9d81eea94..b292e5ca0b7d 100644 --- a/kernel/stackleak.c +++ b/kernel/stackleak.c @@ -27,10 +27,11 @@ static int stack_erasing_sysctl(struct ctl_table *table, int write, int ret = 0; int state = !static_branch_unlikely(&stack_erasing_bypass); int prev_state = state; + struct ctl_table tmp = *table;
- table->data = &state; - table->maxlen = sizeof(int); - ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + tmp.data = &state; + tmp.maxlen = sizeof(int); + ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); state = !!state; if (ret || !write || state == prev_state) return ret;
--- base-commit: f03359bca01bf4372cf2c118cd9a987a5951b1c8 change-id: 20240503-sysctl-const-stackleak-af3e67bc65b0
Best regards,