linux-kernel - [PATCH] comedi: Fix memory leak in compat

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Date:   Thu, 16 Sep 2021 15:44:38 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     linux-kernel@...r.kernel.org
Cc:     Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Greg Kroah-Hartman <greglh@...uxfoundation.org>,
        linux-staging@...ts.linux.dev, stable@...r.kernel.org
Subject: [PATCH] comedi: Fix memory leak in compat_insnlist()

`compat_insnlist()` handles the 32-bit version of the `COMEDI_INSNLIST`
ioctl (whenwhen `CONFIG_COMPAT` is enabled).  It allocates memory to
temporarily hold an array of `struct comedi_insn` converted from the
32-bit version in user space.  This memory is only being freed if there
is a fault while filling the array, otherwise it is leaked.

Add a call to `kfree()` to fix the leak.

Fixes: b8d47d881305 ("comedi: get rid of compat_alloc_user_space() mess in COMEDI_INSNLIST compat"
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Greg Kroah-Hartman <greglh@...uxfoundation.org>
Cc: linux-staging@...ts.linux.dev
Cc: <stable@...r.kernel.org> # 5.13+
Signed-off-by: Ian Abbott <abbotti@....co.uk>
---
N.B. Also need patches for 5.8+ from before comedi moved out of staging.
---
 drivers/comedi/comedi_fops.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c
index df77b6bf5c64..763cea8418f8 100644
--- a/drivers/comedi/comedi_fops.c
+++ b/drivers/comedi/comedi_fops.c
@@ -3090,6 +3090,7 @@ static int compat_insnlist(struct file *file, unsigned long arg)
 	mutex_lock(&dev->mutex);
 	rc = do_insnlist_ioctl(dev, insns, insnlist32.n_insns, file);
 	mutex_unlock(&dev->mutex);
+	kfree(insns);
 	return rc;
 }
 
-- 
2.33.0