linux-kernel - [RFC PATCH v2 2/4] mm/madvise: split out madvise input validity check

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Message-Id: <20250117013058.1843-3-sj@kernel.org>
Date: Thu, 16 Jan 2025 17:30:56 -0800
From: SeongJae Park <sj@...nel.org>
To: 
Cc: SeongJae Park <sj@...nel.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [RFC PATCH v2 2/4] mm/madvise: split out madvise input validity check

Split out the madvise parameters validation logic from do_madvise(), for
easy reuse of the logic from a future change.

Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/madvise.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index ae0964bc4d88..9cc31efe875a 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1592,6 +1592,27 @@ static void madvise_unlock(struct mm_struct *mm, int behavior)
 		mmap_read_unlock(mm);
 }
 
+static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
+{
+	size_t len;
+
+	if (!madvise_behavior_valid(behavior))
+		return false;
+
+	if (!PAGE_ALIGNED(start))
+		return false;
+	len = PAGE_ALIGN(len_in);
+
+	/* Check to see whether len was rounded up from small -ve to zero */
+	if (len_in && !len)
+		return false;
+
+	if (start + len < start)
+		return false;
+
+	return true;
+}
+
 /*
  * The madvise(2) system call.
  *
@@ -1671,20 +1692,11 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
 	size_t len;
 	struct blk_plug plug;
 
-	if (!madvise_behavior_valid(behavior))
+	if (!is_valid_madvise(start, len_in, behavior))
 		return -EINVAL;
 
-	if (!PAGE_ALIGNED(start))
-		return -EINVAL;
 	len = PAGE_ALIGN(len_in);
-
-	/* Check to see whether len was rounded up from small -ve to zero */
-	if (len_in && !len)
-		return -EINVAL;
-
 	end = start + len;
-	if (end < start)
-		return -EINVAL;
 
 	if (end == start)
 		return 0;
-- 
2.39.5