Subject: [PATCH 2937/2944] seq_file: disallow extremely large seq buffer allocations

From: Eric Sandeen <[email-masked]>
Date: Tue, 13 Jul 2021 17:49:23 +0200

fix #35703298

commit 8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b upstream.

There is no reasonable need for a buffer larger than this, and it avoids
int overflow pitfalls.

Fixes: 058504edd026 ("fs/seq_file: fallback to vmalloc allocation")
Suggested-by: Al Viro <[email-masked]>
Reported-by: Qualys Security Advisory <[email-masked]>
Signed-off-by: Eric Sandeen <[email-masked]>
Cc: [email-masked]
Signed-off-by: Linus Torvalds <[email-masked]>

Fixes: CVE-2021-33909
Signed-off-by: Shile Zhang <[email-masked]>
Reviewed-by: Tianjia Zhang <[email-masked]>
Reviewed-by: Joseph Qi <[email-masked]>
---
 fs/seq_file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 05e58b5..e11f62b 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -29,6 +29,9 @@ static void seq_set_overflow(struct seq_file *m)
 
 static void *seq_buf_alloc(unsigned long size)
 {
+	if (unlikely(size > MAX_RW_COUNT))
+		return NULL;
+
 	return kvmalloc(size, GFP_KERNEL_ACCOUNT);
 }
 
-- 
1.8.3.1