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c0a40097f0
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:
|
||
|---|---|---|
| .. | ||
| firmware_loader | ||
| power | ||
| regmap | ||
| test | ||
| arch_numa.c | ||
| arch_topology.c | ||
| attribute_container.c | ||
| auxiliary.c | ||
| base.h | ||
| bus.c | ||
| cacheinfo.c | ||
| class.c | ||
| component.c | ||
| container.c | ||
| core.c | ||
| cpu.c | ||
| dd.c | ||
| devcoredump.c | ||
| devres.c | ||
| devtmpfs.c | ||
| driver.c | ||
| firmware.c | ||
| hypervisor.c | ||
| init.c | ||
| isa.c | ||
| Kconfig | ||
| Makefile | ||
| map.c | ||
| memory.c | ||
| module.c | ||
| node.c | ||
| physical_location.c | ||
| physical_location.h | ||
| pinctrl.c | ||
| platform-msi.c | ||
| platform.c | ||
| property.c | ||
| soc.c | ||
| swnode.c | ||
| syscore.c | ||
| topology.c | ||
| trace.c | ||
| trace.h | ||
| transport_class.c | ||