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Input: synaptics-rmi4 - really fix attn_data use-after-free

Fix a use-after-free noticed by running with KASAN enabled. If
rmi_irq_fn() is run twice in a row, then rmi_f11_attention() (among
others) will end up reading from drvdata->attn_data.data, which was
freed and left dangling in rmi_irq_fn().

Commit 55edde9fff1a ("Input: synaptics-rmi4 - prevent UAF reported by
KASAN") correctly identified and analyzed this bug. However the attempted
fix only NULLed out a local variable, missing the fact that
drvdata->attn_data is a struct, not a pointer.

NULL out the correct pointer in the driver data to prevent the attention
functions from copying from it.

Fixes: 55edde9fff1a ("Input: synaptics-rmi4 - prevent UAF reported by KASAN")
Fixes: b908d3cd812a ("Input: synaptics-rmi4 - allow to add attention data")
Signed-off-by: Evan Green <evgreen@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200427145537.1.Ic8f898e0147beeee2c005ee7b20f1aebdef1e7eb@changeid
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

authored by

Evan Green and committed by
Dmitry Torokhov d5a5e5b5 2712c91a

+1 -1
+1 -1
drivers/input/rmi4/rmi_driver.c
··· 205 205 206 206 if (count) { 207 207 kfree(attn_data.data); 208 - attn_data.data = NULL; 208 + drvdata->attn_data.data = NULL; 209 209 } 210 210 211 211 if (!kfifo_is_empty(&drvdata->attn_fifo))