From: Scott Branden <scott.branden@broadcom.com>
To: Luis Chamberlain <mcgrof@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andy Gross <andy.gross@linaro.org>,
David Brown <david.brown@linaro.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Shuah Khan <shuah@kernel.org>,
bjorn.andersson@linaro.org
Cc: "Rafael J . Wysocki" <rafael@kernel.org>,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
Olof Johansson <olof@lixom.net>,
Andrew Morton <akpm@linux-foundation.org>,
Dan Carpenter <dan.carpenter@oracle.com>,
Colin Ian King <colin.king@canonical.com>,
Kees Cook <keescook@chromium.org>, Takashi Iwai <tiwai@suse.de>,
linux-kselftest@vger.kernel.org,
Scott Branden <scott.branden@broadcom.com>
Subject: [PATCH 3/3] firmware: add mutex fw_lock_fallback for race condition
Date: Thu, 15 Aug 2019 17:09:45 -0700 [thread overview]
Message-ID: <20190816000945.29810-4-scott.branden@broadcom.com> (raw)
In-Reply-To: <20190816000945.29810-1-scott.branden@broadcom.com>
A race condition exists between _request_firmware_prepare checking
if firmware is assigned and firmware_fallback_sysfs creating a sysfs
entry (kernel trace below). To avoid such condition add a mutex
fw_lock_fallback to protect against such condition.
misc test_firmware: Falling back to sysfs fallback for: nope-test-firmware.bin
sysfs: cannot create duplicate filename '/devices/virtual/misc/test_firmware/nope-test-firmware.bin'
CPU: 4 PID: 2059 Comm: test_firmware-3 Not tainted 5.3.0-rc4 #1
Hardware name: Dell Inc. OptiPlex 7010/0KRC95, BIOS A13 03/25/2013
Call Trace:
dump_stack+0x67/0x90
sysfs_warn_dup.cold+0x17/0x24
sysfs_create_dir_ns+0xb3/0xd0
kobject_add_internal+0xa6/0x2a0
kobject_add+0x7e/0xb0
? _cond_resched+0x15/0x30
device_add+0x121/0x670
firmware_fallback_sysfs+0x15c/0x3c9
_request_firmware+0x432/0x5a0
? devres_find+0x63/0xc0
request_firmware_into_buf+0x63/0x80
test_fw_run_batch_request+0x96/0xe0
kthread+0xfb/0x130
? reset_store+0x30/0x30
? kthread_park+0x80/0x80
ret_from_fork+0x3a/0x50
kobject_add_internal failed for nope-test-firmware.bin with -EEXIST, don't try to register things with the same name in the same directory.
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
---
drivers/base/firmware_loader/main.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index bf44c79beae9..ce9896e3b782 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -88,6 +88,7 @@ static inline struct fw_priv *to_fw_priv(struct kref *ref)
/* fw_lock could be moved to 'struct fw_sysfs' but since it is just
* guarding for corner cases a global lock should be OK */
DEFINE_MUTEX(fw_lock);
+DEFINE_MUTEX(fw_lock_fallback);
static struct firmware_cache fw_cache;
@@ -758,6 +759,17 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
if (!firmware_p)
return -EINVAL;
+ /*
+ * There is a race condition between _request_firmware_prepare checking
+ * if firmware is assigned and firmware_fallback_sysfs creating sysfs
+ * entries with duplicate names.
+ * Yet, with this lock the firmware_test locks up with cache enabled
+ * and no event used during firmware test.
+ * This points to some very racy code I don't know how to entirely fix.
+ */
+ if (opt_flags & FW_OPT_NOCACHE)
+ mutex_lock(&fw_lock_fallback);
+
if (!name || name[0] == '\0') {
ret = -EINVAL;
goto out;
@@ -791,6 +803,9 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
fw = NULL;
}
+ if (opt_flags & FW_OPT_NOCACHE)
+ mutex_unlock(&fw_lock_fallback);
+
*firmware_p = fw;
return ret;
}
--
2.17.1
next prev parent reply other threads:[~2019-08-16 0:10 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 0:09 [PATCH 0/3] firmware: selftest for request_firmware_into_buf Scott Branden
2019-08-16 0:09 ` [PATCH 1/3] test_firmware: add support " Scott Branden
2019-08-19 5:24 ` Luis Chamberlain
2019-08-19 20:27 ` shuah
2019-08-16 0:09 ` [PATCH 2/3] selftest: firmware: Add request_firmware_into_buf tests Scott Branden
2019-08-19 5:24 ` Luis Chamberlain
2019-08-19 20:27 ` shuah
2019-08-16 0:09 ` Scott Branden [this message]
2019-08-19 5:39 ` [PATCH 3/3] firmware: add mutex fw_lock_fallback for race condition Luis Chamberlain
2019-08-19 16:19 ` Scott Branden
2019-08-20 1:26 ` Luis Chamberlain
2019-08-20 15:54 ` Scott Branden
2019-08-23 10:31 ` Takashi Iwai
2019-08-23 15:43 ` Luis Chamberlain
2019-08-23 19:56 ` Scott Branden
2019-08-23 19:48 ` Scott Branden
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