[PATCH] mm: huge_memory: Handle strsep not finding delimiter

[Leo Stone <leocstone@gmail.com>]

split_huge_pages_write does not handle the case where strsep finds no
delimiter in the given string and sets the input buffer to NULL,
which allows this reproducer to trigger a protection fault.

Reported-by: syzbot+8a3da2f1bbf59227c289@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8a3da2f1bbf59227c289
Signed-off-by: Leo Stone <leocstone@gmail.com>
---
 mm/huge_memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ee335d96fc39..361319f749f0 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4168,7 +4168,7 @@ static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
 		size_t input_len = strlen(input_buf);
 
 		tok = strsep(&buf, ",");
-		if (tok) {
+		if (tok && buf) {
 			strscpy(file_path, tok);
 		} else {
 			ret = -EINVAL;
-- 
2.43.0