From ef9d965bc8b6fce5bcc0ae76a4a5b3ed91ee81eb Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 9 Jun 2020 19:08:19 +0200
Subject: [PATCH] sysctl: reject gigantic reads/write to sysctl files
Instead of triggering a WARN_ON deep down in the page allocator just
give up early on allocations that are way larger than the usual sysctl
values.
Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/proc/proc_sysctl.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index df2143e05c571..08c33bd1642dc 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -564,6 +564,10 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
if (!table->proc_handler)
goto out;
+ /* don't even try if the size is too large */
+ if (count > KMALLOC_MAX_SIZE)
+ return -ENOMEM;
+
if (write) {
kbuf = memdup_user_nul(ubuf, count);
if (IS_ERR(kbuf)) {
--
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