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mm: debug_page_alloc: fix NULL buf in debug_guardpage_minorder_setup

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If the kernel command line includes "debug_guardpage_minorder" without an
equals sign (i.e., no value is provided), the early parameter parser
passes a NULL buf pointer to the setup function.

kstrtouint() does not perform a NULL check on its input and calls directly
into kstrtoull() which dereferences s[0] unconditionally, leading to a
NULL pointer dereference and early boot crash.

Additionally, the error path's pr_err("%s", buf) would also crash with a
NULL format argument.

Link: https://lore.kernel.org/20260806004556.2633049-1-ye.liu@linux.dev
Fixes: c0a32fc5a2 ("mm: more intensive memory corruption debugging")
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ye Liu 2026-08-06 08:45:55 +08:00 committed by Andrew Morton
parent 4b82a0b91b
commit 54cc9b3847
1 changed files with 2 additions and 2 deletions
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4
mm/debug_page_alloc.c
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@ -22,8 +22,8 @@ static int __init debug_guardpage_minorder_setup(char *buf)
{
unsigned int res;
if (kstrtouint(buf, 10, &res) < 0 || res > MAX_PAGE_ORDER / 2) {
pr_err("Bad debug_guardpage_minorder value: %s\n", buf);
if (!buf || kstrtouint(buf, 10, &res) < 0 || res > MAX_PAGE_ORDER / 2) {
pr_err("Bad debug_guardpage_minorder value: %s\n", buf ?: "(missing)");
return 0;
}
_debug_guardpage_minorder = res;