linux-kernel - [PATCH] staging: ion: WARN when the handle kmap

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: <1400806281-32716-1-git-send-email-mitchelh@codeaurora.org>
Date:	Thu, 22 May 2014 17:51:21 -0700
From:	Mitchel Humpherys <mitchelh@...eaurora.org>
To:	linux-mm@...ck.org, Colin Cross <ccross@...roid.com>,
	John Stultz <john.stultz@...aro.org>
Cc:	Android Kernel Team <kernel-team@...roid.com>,
	linux-kernel@...r.kernel.org,
	Mitchel Humpherys <mitchelh@...eaurora.org>
Subject: [PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around

There are certain client bugs (double unmap, for example) that can cause
the handle->kmap_cnt (an unsigned int) to wrap around from zero. This
causes problems when the handle is destroyed because we have:

        while (handle->kmap_cnt)
                ion_handle_kmap_put(handle);

which takes a long time to complete when kmap_cnt starts at ~0 and can
result in a watchdog timeout.

WARN and bail when kmap_cnt is about to wrap around from zero.

Signed-off-by: Mitchel Humpherys <mitchelh@...eaurora.org>
---
 drivers/staging/android/ion/ion.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 3d5bf14722..f55f61a4cc 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -626,6 +626,10 @@ static void ion_handle_kmap_put(struct ion_handle *handle)
 {
 	struct ion_buffer *buffer = handle->buffer;
 
+	if (!handle->kmap_cnt) {
+		WARN(1, "%s: Double unmap detected! bailing...\n", __func__);
+		return;
+	}
 	handle->kmap_cnt--;
 	if (!handle->kmap_cnt)
 		ion_buffer_kmap_put(buffer);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/