mm: debug_page_alloc: fix NULL buf in debug_guardpage_minorder_setup

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: c0a32fc5a2e4 ("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>

0 files changed, 0 insertions, 0 deletions