[PATCH 6.18 170/309] sysctl: fix uninitialized variable in proc_do_large_bitmap

Greg Kroah-Hartman
2026-03-31T17:05:24Z

From: Marc Buerg <buermarc@googlemail.com>

[ Upstream commit f63a9df7e3f9f842945d292a19d9938924f066f9 ]

proc_do_large_bitmap() does not initialize variable c, which is expected
to be set to a trailing character by proc_get_long().

However, proc_get_long() only sets c when the input buffer contains a
trailing character after the parsed value.

If c is not initialized it may happen to contain a '-'. If this is the
case proc_do_large_bitmap() expects to be able to parse a second part of
the input buffer. If there is no second part an unjustified -EINVAL will
be returned.

Initialize c to 0 to prevent returning -EINVAL on valid input.

Fixes: 9f977fb7ae9d ("sysctl: add proc_do_large_bitmap")
Signed-off-by: Marc Buerg <buermarc@googlemail.com>
Reviewed-by: Joel Granados <joel.granados@kernel.org>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/sysctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cb6196e3fa993..970525e6c76c7 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1213,7 +1213,7 @@ int proc_do_large_bitmap(const struct ctl_table *table, int write,
unsigned long bitmap_len = table->maxlen;
unsigned long *bitmap = *(unsigned long **) table->data;
unsigned long *tmp_bitmap = NULL;
- char tr_a[] = { '-', ',', '\n' }, tr_b[] = { ',', '\n', 0 }, c;
+ char tr_a[] = { '-', ',', '\n' }, tr_b[] = { ',', '\n', 0 }, c = 0;

if (!bitmap || !bitmap_len || !left || (*ppos && !write)) {
*lenp = 0;
--
2.53.0