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Message-Id: <20241003-fix-null-deref-v1-1-0a45df9d016a@iiitd.ac.in>
Date: Thu, 03 Oct 2024 21:31:06 +0530
From: Manas via B4 Relay <devnull+manas18244.iiitd.ac.in@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Peter Xu <peterx@...hat.com>, Shuah Khan <skhan@...uxfoundation.org>,
Anup Sharma <anupnewsmail@...il.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
syzbot+093d096417e7038a689b@...kaller.appspotmail.com,
Manas <manas18244@...td.ac.in>
Subject: [PATCH] Fixes: null pointer dereference in pfnmap_lockdep_assert
From: Manas <manas18244@...td.ac.in>
syzbot has pointed to a possible null pointer dereference in
pfnmap_lockdep_assert. vm_file member of vm_area_struct is being
dereferenced without any checks.
This fix returns if vm_file member in vm_area_struct is NULL.
Reported-by: syzbot+093d096417e7038a689b@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
---
This bug[1] triggers a general protection fault in follow_pfnmap_start
function. An assertion pfnmap_lockdep_assert inside this function
dereferences vm_file member of vm_area_struct. And panic gets triggered
when vm_file is NULL.
This patch returns from the assertion pfnmap_lockdep_assert if vm_file
is found to be NULL.
[1] https://syzkaller.appspot.com/bug?extid=093d096417e7038a689b
Signed-off-by: Manas <manas18244@...td.ac.in>
---
mm/memory.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c
index 2366578015ad..b152a95e543f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6346,6 +6346,9 @@ static inline void pfnmap_args_setup(struct follow_pfnmap_args *args,
static inline void pfnmap_lockdep_assert(struct vm_area_struct *vma)
{
#ifdef CONFIG_LOCKDEP
+ if (!vma->vm_file)
+ return;
+
struct address_space *mapping = vma->vm_file->f_mapping;
if (mapping)
---
base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
change-id: 20241003-fix-null-deref-6bfa0337efc3
Best regards,
--
Manas <manas18244@...td.ac.in>
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