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i2c: dev: prevent integer overflow in I2C_TIMEOUT ioctl

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While fuzzing with Syzkaller, a persistent `schedule_timeout: wrong
timeout value` warning was observed, accompanied by SMBus controller
state machine corruption.

The I2C_TIMEOUT ioctl accepts a user-provided timeout in multiples of
10 ms. The user argument is checked against INT_MAX, but it is
subsequently multiplied by 10 before being passed to msecs_to_jiffies().

A malicious user can pass a large value (e.g., 429496729) that passes
the `arg > INT_MAX` check but overflows when multiplied by 10. This
results in a truncated 32-bit unsigned value that bypasses the
internal `(int)m < 0` check in `msecs_to_jiffies()`.

The truncated value is then assigned to `client->adapter->timeout`
(a signed 32-bit int), which is reinterpreted as a negative number.
When passed to wait_for_completion_timeout(), this negative value
undergoes sign extension to a 64-bit unsigned long, triggering the
`schedule_timeout` warning and causing premature returns. This leaves
the SMBus state machine in an unrecoverable state, constituting a
local Denial of Service (DoS).

Fix this by bounding the user argument to `INT_MAX / 10`.

Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn>
[wsa: move the comment as well]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
This commit is contained in:
Mingyu Wang 2026-04-27 10:57:45 +08:00 committed by Wolfram Sang
parent 9998e388be
commit 617eb7c096
1 changed files with 5 additions and 4 deletions
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9
drivers/i2c/i2c-dev.c
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@ -487,12 +487,13 @@ static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
client->adapter->retries = arg;
break;
case I2C_TIMEOUT:
if (arg > INT_MAX)
/*
* For historical reasons, user-space sets the timeout value in
* units of 10 ms.
*/
if (arg > INT_MAX / 10)
return -EINVAL;
/* For historical reasons, user-space sets the timeout
* value in units of 10 ms.
*/
client->adapter->timeout = msecs_to_jiffies(arg * 10);
break;
default: