unimore/kernel-hacking-2024-linux-steffo
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Input: psmouse - fix data race in __ps2_command

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The data race happens on ps2dev->cmdcnt and ps2dev->cmdbuf contents.
__ps2_command reads that data concurrently with the interrupt handler. As
the result, for example, if a response arrives just after the timeout,
__ps2_command can copy out garbage from ps2dev->cmdbuf but then see that
ps2dev->cmdcnt is 0 and return success.

Stop the interrupt handler with serio_pause_rx() before reading the
results.

The data race was found with KernelThreadSanitizer (KTSAN).

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
This commit is contained in:
Dmitry Vyukov 2015-09-29 15:54:58 -07:00 committed by Dmitry Torokhov
parent 22ef28b43f
commit 218c1f76b8
1 changed files with 14 additions and 8 deletions
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22
drivers/input/serio/libps2.c
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@ -212,12 +212,17 @@ int __ps2_command(struct ps2dev *ps2dev, unsigned char *param, int command)
* time before the ACK arrives.
*/
if (ps2_sendbyte(ps2dev, command & 0xff,
command == PS2_CMD_RESET_BAT ? 1000 : 200))
goto out;
command == PS2_CMD_RESET_BAT ? 1000 : 200)) {
serio_pause_rx(ps2dev->serio);
goto out_reset_flags;
}
for (i = 0; i < send; i++)
if (ps2_sendbyte(ps2dev, param[i], 200))
goto out;
for (i = 0; i < send; i++) {
if (ps2_sendbyte(ps2dev, param[i], 200)) {
serio_pause_rx(ps2dev->serio);
goto out_reset_flags;
}
}
/*
* The reset command takes a long time to execute.
@ -234,17 +239,18 @@ int __ps2_command(struct ps2dev *ps2dev, unsigned char *param, int command)
!(ps2dev->flags & PS2_FLAG_CMD), timeout);
}
serio_pause_rx(ps2dev->serio);
if (param)
for (i = 0; i < receive; i++)
param[i] = ps2dev->cmdbuf[(receive - 1) - i];
if (ps2dev->cmdcnt && (command != PS2_CMD_RESET_BAT || ps2dev->cmdcnt != 1))
goto out;
goto out_reset_flags;
rc = 0;
out:
serio_pause_rx(ps2dev->serio);
out_reset_flags:
ps2dev->flags = 0;
serio_continue_rx(ps2dev->serio);