[PATCH v3 1/4] mm/hugetlb_cma: fix incorrect hugetlb_cma_size assignment on malformed input

[Kaitao Cheng <kaitao.cheng@linux.dev>]

From: Kaitao Cheng <chengkaitao@kylinos.cn>

When hugetlb_cma contains a global size after node-specific entries,
cmdline_parse_hugetlb_cma() enters the global branch and reparses the
original parameter string. For hugetlb_cma=1:2G,4G, this interprets the
initial node ID as a one-byte global size and clears the 2 GiB reservation
recorded for node 1.

Global and node-specific formats cannot be mixed. Return -EINVAL when a
global entry follows a node-specific entry, before updating any settings.
This preserves the valid prefix, so the example retains node 1's 2 GiB
reservation and reports the malformed option.

Fixes: 38e719ab2673 ("hugetlb: support node specified when using cma for gigantic hugepages")
Closes: https://sashiko.dev/#/bug/linux-10f40d3e-3feb-4622-9da8-1fedecb2d0e2
Acked-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
---
 mm/hugetlb_cma.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/hugetlb_cma.c b/mm/hugetlb_cma.c
index 80b2407e9f07..cd6a64986278 100644
--- a/mm/hugetlb_cma.c
+++ b/mm/hugetlb_cma.c
@@ -165,6 +165,9 @@ static int __init cmdline_parse_hugetlb_cma(char *p)
 		} else {
 			char *next;
 
+			if (s != p)
+				return -EINVAL;
+
 			tmp = memparse(p, &next);
 			if (*next == '%') {
 				if (tmp > 100) {
-- 
2.53.0