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| Filename | Latest commit message | Latest commit date |
|---|---|---|
13d25e82b6
commit c0a40097f0bc81deafc15f9195d1fb54595cd6d0 upstream.
Synchronize the dev->driver usage in really_probe() and dev_uevent().
These can run in different threads, what can result in the following
race condition for dev->driver uninitialization:
Thread #1:
==========
really_probe() {
...
probe_failed:
...
device_unbind_cleanup(dev) {
...
dev->driver = NULL; // <= Failed probe sets dev->driver to NULL
...
}
...
}
Thread #2:
==========
dev_uevent() {
...
if (dev->driver)
// If dev->driver is NULLed from really_probe() from here on,
// after above check, the system crashes
add_uevent_var(env, "DRIVER=%s", dev->driver->name);
...
}
really_probe() holds the lock, already. So nothing needs to be done
there. dev_uevent() is called with lock held, often, too. But not
always. What implies that we can't add any locking in dev_uevent()
itself. So fix this race by adding the lock to the non-protected
path. This is the path where above race is observed:
dev_uevent+0x235/0x380
uevent_show+0x10c/0x1f0 <= Add lock here
dev_attr_show+0x3a/0xa0
sysfs_kf_seq_show+0x17c/0x250
kernfs_seq_show+0x7c/0x90
seq_read_iter+0x2d7/0x940
kernfs_fop_read_iter+0xc6/0x310
vfs_read+0x5bc/0x6b0
ksys_read+0xeb/0x1b0
__x64_sys_read+0x42/0x50
x64_sys_call+0x27ad/0x2d30
do_syscall_64+0xcd/0x1d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Similar cases are reported by syzkaller in
https://syzkaller.appspot.com/bug?extid=ffa8143439596313a85a
But these are regarding the *initialization* of dev->driver
dev->driver = drv;
As this switches dev->driver to non-NULL these reports can be considered
to be false-positives (which should be "fixed" by this commit, as well,
though).
The same issue was reported and tried to be fixed back in 2015 in
https://lore.kernel.org/lkml/1421259054-2574-1-git-send-email-a.sangwan@samsung.com/
already.
Fixes:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| 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.