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993db6da4a
[ Upstream commit 0cea730cac ]
In service_callback path RCU dereferenced pointer struct vchiq_service
need to be accessed inside rcu read-critical section.
Also userdata/user_service part of vchiq_service is accessed around
different synchronization mechanism, getting an extra reference to a
pointer keeps sematics simpler and avoids prolonged graceperiod.
Accessing vchiq_service with rcu_read_[lock/unlock] fixes below issue.
[ 32.201659] =============================
[ 32.201664] WARNING: suspicious RCU usage
[ 32.201670] 5.15.11-rt24-v8+ #3 Not tainted
[ 32.201680] -----------------------------
[ 32.201685] drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h:529 suspicious rcu_dereference_check() usage!
[ 32.201695]
[ 32.201695] other info that might help us debug this:
[ 32.201695]
[ 32.201700]
[ 32.201700] rcu_scheduler_active = 2, debug_locks = 1
[ 32.201708] no locks held by vchiq-slot/0/98.
[ 32.201715]
[ 32.201715] stack backtrace:
[ 32.201723] CPU: 1 PID: 98 Comm: vchiq-slot/0 Not tainted 5.15.11-rt24-v8+ #3
[ 32.201733] Hardware name: Raspberry Pi 4 Model B Rev 1.4 (DT)
[ 32.201739] Call trace:
[ 32.201742] dump_backtrace+0x0/0x1b8
[ 32.201772] show_stack+0x20/0x30
[ 32.201784] dump_stack_lvl+0x8c/0xb8
[ 32.201799] dump_stack+0x18/0x34
[ 32.201808] lockdep_rcu_suspicious+0xe4/0xf8
[ 32.201817] service_callback+0x124/0x400
[ 32.201830] slot_handler_func+0xf60/0x1e20
[ 32.201839] kthread+0x19c/0x1a8
[ 32.201849] ret_from_fork+0x10/0x20
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
Link: https://lore.kernel.org/r/20211231195406.5479-1-treasure4paddy@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
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In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.