linux-kernel - [PATCH v2] usb: mon: Fix atomicity violation in mon_bin_vma

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20231222060450.5449-1-2045gemini@gmail.com>
Date: Fri, 22 Dec 2023 14:04:50 +0800
From: Gui-Dong Han <2045gemini@...il.com>
To: gregkh@...uxfoundation.org,
	surenb@...gle.com,
	42.hyeyoo@...il.com,
	benjamin.tissoires@...hat.com,
	mhocko@...e.com,
	ivan.orlov0322@...il.com
Cc: linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	baijiaju1990@...look.com,
	Gui-Dong Han <2045gemini@...il.com>,
	stable@...r.kernel.org,
	BassCheck <bass@...a.edu.cn>
Subject: [PATCH v2] usb: mon: Fix atomicity violation in mon_bin_vma_fault

In mon_bin_vma_fault():
	offset = vmf->pgoff << PAGE_SHIFT;
	if (offset >= rp->b_size)
		return VM_FAULT_SIGBUS;
	chunk_idx = offset / CHUNK_SIZE;
	pageptr = rp->b_vec[chunk_idx].pg;
The code is executed without holding any lock.

In mon_bin_vma_close():
	spin_lock_irqsave(&rp->b_lock, flags);
	rp->mmap_active--;
	spin_unlock_irqrestore(&rp->b_lock, flags);

In mon_bin_ioctl():
	spin_lock_irqsave(&rp->b_lock, flags);
	if (rp->mmap_active) {
		...
	} else {
		...
		kfree(rp->b_vec);
		rp->b_vec  = vec;
		rp->b_size = size;
		...
	}
	spin_unlock_irqrestore(&rp->b_lock, flags);

Concurrent execution of mon_bin_vma_fault() with mon_bin_vma_close() and
mon_bin_ioctl() could lead to atomicity violations. mon_bin_vma_fault()
accesses rp->b_size and rp->b_vec without locking, risking array
out-of-bounds access or use-after-free bugs due to possible modifications
in mon_bin_ioctl().

This possible bug is found by an experimental static analysis tool
developed by our team, BassCheck[1]. This tool analyzes the locking APIs
to extract function pairs that can be concurrently executed, and then
analyzes the instructions in the paired functions to identify possible
concurrency bugs including data races and atomicity violations. The above
possible bug is reported when our tool analyzes the source code of
Linux 6.2.

To address this issue, it is proposed to add a spin lock pair in
mon_bin_vma_fault() to ensure atomicity. With this patch applied, our tool
never reports the possible bug, with the kernel configuration allyesconfig
for x86_64. Due to the lack of associated hardware, we cannot test the
patch in runtime testing, and just verify it according to the code logic.

[1] https://sites.google.com/view/basscheck/

Fixes: 19e6317d24c25 ("usb: mon: Fix a deadlock in usbmon between ...")
Cc: stable@...r.kernel.org
Reported-by: BassCheck <bass@...a.edu.cn>
Signed-off-by: Gui-Dong Han <2045gemini@...il.com>
---
v2:
* In this patch v2, we've added some information of the static analysis
tool used, as per the researcher guidelines. Also, we've added a cc in the
signed-off-by area, according to the stable-kernel-rules.
  Thank Greg KH for helpful advice.
---
 drivers/usb/mon/mon_bin.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/mon/mon_bin.c b/drivers/usb/mon/mon_bin.c
index 9ca9305243fe..509cd1b8ff13 100644
--- a/drivers/usb/mon/mon_bin.c
+++ b/drivers/usb/mon/mon_bin.c
@@ -1250,12 +1250,16 @@ static vm_fault_t mon_bin_vma_fault(struct vm_fault *vmf)
 	struct mon_reader_bin *rp = vmf->vma->vm_private_data;
 	unsigned long offset, chunk_idx;
 	struct page *pageptr;
-
+	unsigned long flags;
+	spin_lock_irqsave(&rp->b_lock, flags);
 	offset = vmf->pgoff << PAGE_SHIFT;
-	if (offset >= rp->b_size)
+	if (offset >= rp->b_size) {
+		spin_unlock_irqrestore(&rp->b_lock, flags);
 		return VM_FAULT_SIGBUS;
+	}
 	chunk_idx = offset / CHUNK_SIZE;
 	pageptr = rp->b_vec[chunk_idx].pg;
+	spin_unlock_irqrestore(&rp->b_lock, flags);
 	get_page(pageptr);
 	vmf->page = pageptr;
 	return 0;
-- 
2.34.1