linux-kernel - [PATCH] soc: apple: rtkit: Fix use-after-free in apple_rtkit_crashlog

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Message-ID: <20250212085853.1357906-1-harshit.m.mogalapalli@oracle.com>
Date: Wed, 12 Feb 2025 00:58:53 -0800
From: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To: Sven Peter <sven@...npeter.dev>, Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Janne Grunau <j@...nau.net>, Asahi Lina <lina@...hilina.net>,
        Jens Axboe <axboe@...nel.dk>, asahi@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
        error27@...il.com, harshit.m.mogalapalli@...cle.com
Subject: [PATCH] soc: apple: rtkit: Fix use-after-free in apple_rtkit_crashlog_rx()

This code calls kfree(bfr); and then passes "bfr" to rtk->ops->crashed()
which is a use after free.  The ->crashed function pointer is implemented
by apple_nvme_rtkit_crashed() and it doesn't use the "bfr" pointer so
this doesn't cause a problem.  But it still looks sketchy as can be.

Fix this by moving kfree() after the last usage of bfr.

Fixes: c559645f343a ("soc: apple: rtkit: Pass the crashlog to the crashed() callback")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
---
This is based on static analysis with smatch, only compile tested.
---
 drivers/soc/apple/rtkit.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c
index 4b0783091a92..1ccec7ba640c 100644
--- a/drivers/soc/apple/rtkit.c
+++ b/drivers/soc/apple/rtkit.c
@@ -360,7 +360,6 @@ static void apple_rtkit_crashlog_rx(struct apple_rtkit *rtk, u64 msg)
 		apple_rtkit_memcpy(rtk, bfr, &rtk->crashlog_buffer, 0,
 				   rtk->crashlog_buffer.size);
 		apple_rtkit_crashlog_dump(rtk, bfr, rtk->crashlog_buffer.size);
-		kfree(bfr);
 	} else {
 		dev_err(rtk->dev,
 			"RTKit: Couldn't allocate crashlog shadow buffer\n");
@@ -369,6 +368,8 @@ static void apple_rtkit_crashlog_rx(struct apple_rtkit *rtk, u64 msg)
 	rtk->crashed = true;
 	if (rtk->ops->crashed)
 		rtk->ops->crashed(rtk->cookie, bfr, rtk->crashlog_buffer.size);
+
+	kfree(bfr);
 }
 
 static void apple_rtkit_ioreport_rx(struct apple_rtkit *rtk, u64 msg)
-- 
2.39.3