linux-kernel - [PATCH] usb: host: ehci-sched: avoid possible NULL dereference

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Message-Id: <20201005213149.12332-1-sudipm.mukherjee@gmail.com>
Date:   Mon,  5 Oct 2020 22:31:49 +0100
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-safety@...ts.elisa.tech,
        linux-usb@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH] usb: host: ehci-sched: avoid possible NULL dereference

find_tt() can return NULL or the error value in ERR_PTR() and
dereferencing the return value without checking for the error can
lead to a possible dereference of NULL pointer or ERR_PTR().

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
---
 drivers/usb/host/ehci-sched.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 6dfb242f9a4b..f3fd7e9fe6b2 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -245,6 +245,8 @@ static void reserve_release_intr_bandwidth(struct ehci_hcd *ehci,
 	/* FS/LS bus bandwidth */
 	if (tt_usecs) {
 		tt = find_tt(qh->ps.udev);
+		if (IS_ERR_OR_NULL(tt))
+			return;
 		if (sign > 0)
 			list_add_tail(&qh->ps.ps_list, &tt->ps_list);
 		else
@@ -1338,6 +1340,8 @@ static void reserve_release_iso_bandwidth(struct ehci_hcd *ehci,
 		}
 
 		tt = find_tt(stream->ps.udev);
+		if (IS_ERR_OR_NULL(tt))
+			return;
 		if (sign > 0)
 			list_add_tail(&stream->ps.ps_list, &tt->ps_list);
 		else
-- 
2.11.0