Hi! The currently upstream version of this patch actually breaks
uinput, and causes the kernel to panic when attempting to run it under
qemu using spice. Here's a backtrace from kdb:
Stack traceback for pid 656
0xffff8800babed480 656 1 1 2 R 0xffff8800babefa80
*spice-vdagentd
ffff88013747bd58 0000000000000018 ffff88013747bd80 ffff8800b7977000
0000000000000003 0000000000000001 0000000000000001 ffff8800b7977240
ffff88013747bdc0 ffffffff8163f449 0000000000000286 0000000000000018
Call Trace:
[<ffffffff8163f449>] ? input_event+0x59/0x80
[<ffffffffa0509234>] ? uinput_write+0x154/0x460 [uinput]
[<ffffffffa00e704d>] ? port_fops_read+0xfd/0x1f0 [virtio_console]
[<ffffffff81261627>] ? __vfs_write+0x37/0x100
[<ffffffff81261ff9>] ? vfs_write+0xa9/0x1a0
[<ffffffff81283386>] ? __fget_light+0x66/0x90
[<ffffffff81262cf8>] ? SyS_write+0x58/0xd0
[<ffffffff81833c72>] ? entry_SYSCALL_64_fastpath+0x12/0x76
And the relevant messages from dmesg:
<1>[ 15.064330] BUG: unable to handle kernel NULL pointer dereference at
0000000000000024
<1>[ 15.064336] IP: [<ffffffff8163f142>] input_handle_event+0x232/0x4e0
<4>[ 15.064343] PGD 0
<4>[ 15.064345] Oops: 0000 [#1] SMP
The steps for reproducing this are pretty simple: setup a Fedora 22 VM,
build the latest kernel and install it with make install, and try to
boot the machine and use it over spice with qemu. After moving the
cursor it'll run into a NULL dereference and panic.
I've tested reverting this commit, and that fixes the NULL dereference
completely. I'm willing to git send-email you the revert if wish.
Cheers,
Lyude
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