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|---|---|---|
ea748ebb90
[ Upstream commit 8d63c83d8eb922f6c316320f50c82fa88d099bea ]
Yunseong Kim and the syzbot fuzzer both reported a problem in
RT-enabled kernels caused by the way dummy-hcd mixes interrupt
management and spin-locking. The pattern was:
local_irq_save(flags);
spin_lock(&dum->lock);
...
spin_unlock(&dum->lock);
... // calls usb_gadget_giveback_request()
local_irq_restore(flags);
The code was written this way because usb_gadget_giveback_request()
needs to be called with interrupts disabled and the private lock not
held.
While this pattern works fine in non-RT kernels, it's not good when RT
is enabled. RT kernels handle spinlocks much like mutexes; in particular,
spin_lock() may sleep. But sleeping is not allowed while local
interrupts are disabled.
To fix the problem, rewrite the code to conform to the pattern used
elsewhere in dummy-hcd and other UDC drivers:
spin_lock_irqsave(&dum->lock, flags);
...
spin_unlock(&dum->lock);
usb_gadget_giveback_request(...);
spin_lock(&dum->lock);
...
spin_unlock_irqrestore(&dum->lock, flags);
This approach satisfies the RT requirements.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Fixes:
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
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.