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Dmitry Torokhov 08637180f7 Input: try trimming too long modalias strings
commit 0774d19038c496f0c3602fb505c43e1b2d8eed85 upstream.

If an input device declares too many capability bits then modalias
string for such device may become too long and not fit into uevent
buffer, resulting in failure of sending said uevent. This, in turn,
may prevent userspace from recognizing existence of such devices.

This is typically not a concern for real hardware devices as they have
limited number of keys, but happen with synthetic devices such as
ones created by xen-kbdfront driver, which creates devices as being
capable of delivering all possible keys, since it doesn't know what
keys the backend may produce.

To deal with such devices input core will attempt to trim key data,
in the hope that the rest of modalias string will fit in the given
buffer. When trimming key data it will indicate that it is not
complete by placing "+," sign, resulting in conversions like this:

old: k71,72,73,74,78,7A,7B,7C,7D,8E,9E,A4,AD,E0,E1,E4,F8,174,
new: k71,72,73,74,78,7A,7B,7C,+,

This should allow existing udev rules continue to work with existing
devices, and will also allow writing more complex rules that would
recognize trimmed modalias and check input device characteristics by
other means (for example by parsing KEY= data in uevent or parsing
input device sysfs attributes).

Note that the driver core may try adding more uevent environment
variables once input core is done adding its own, so when forming
modalias we can not use the entire available buffer, so we reduce
it by somewhat an arbitrary amount (96 bytes).

Reported-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Tested-by: Jason Andryuk <jandryuk@gmail.com>
Link: https://lore.kernel.org/r/ZjAWMQCJdrxZkvkB@google.com
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
2024-07-05 09:08:16 +02:00
arch sparc: move struct termio to asm/termios.h 2024-06-16 13:28:52 +02:00
block
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drivers Input: try trimming too long modalias strings 2024-07-05 09:08:16 +02:00
fs jfs: xattr: fix buffer overflow for invalid xattr 2024-07-05 09:08:15 +02:00
include net: fix __dst_negative_advice() race 2024-06-16 13:28:52 +02:00
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net ipv6: fix possible race in __fib6_drop_pcpu_from() 2024-07-05 09:08:13 +02:00
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sound ASoC: ti: davinci-mcasp: Fix race condition during probe 2024-07-05 09:08:13 +02:00
tools selftests/mm: compaction_test: fix bogus test success on Aarch64 2024-07-05 09:08:14 +02:00
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Makefile Linux 5.4.278 2024-06-16 13:28:53 +02:00
README

Linux kernel
============

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There are various text files in the Documentation/ subdirectory,
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