linux-kernel - [PATCH] media: dib8000: Fix a memleak in dib8000

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Date:   Tue, 30 Nov 2021 23:38:05 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Mauro Carvalho Chehab <mchehab@...nel.org>,
        Patrick Boettcher <pboettcher@...com.fr>,
        Olivier Grenie <Olivier.Grenie@...com.fr>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] media: dib8000: Fix a memleak in dib8000_init()

In dib8000_init(), the variable fe is not freed or passed out on the
failure of dib8000_identify(&state->i2c), which could lead to a memleak.

Fix this bug by adding a kfree of fe in the error path.

This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

Builds with CONFIG_DVB_DIB8000=m show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 77e2c0f5d471 ("V4L/DVB (12900): DiB8000: added support for DiBcom ISDB-T/ISDB-Tsb demodulator DiB8000")
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
---
 drivers/media/dvb-frontends/dib8000.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/dvb-frontends/dib8000.c b/drivers/media/dvb-frontends/dib8000.c
index bb02354a48b8..d67f2dd997d0 100644
--- a/drivers/media/dvb-frontends/dib8000.c
+++ b/drivers/media/dvb-frontends/dib8000.c
@@ -4473,8 +4473,10 @@ static struct dvb_frontend *dib8000_init(struct i2c_adapter *i2c_adap, u8 i2c_ad

 	state->timf_default = cfg->pll->timf;

-	if (dib8000_identify(&state->i2c) == 0)
+	if (dib8000_identify(&state->i2c) == 0) {
+		kfree(fe);
 		goto error;
+	}

 	dibx000_init_i2c_master(&state->i2c_master, DIB8000, state->i2c.adap, state->i2c.addr);

-- 
2.25.1