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i2c: core: check returned size of emulated smbus block read

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If the i2c bus driver ignores the I2C_M_RECV_LEN flag (as some of
them do), it is possible for an I2C_SMBUS_BLOCK_DATA read issued
on some random device to return an arbitrary value in the first
byte (and nothing else).  When this happens, i2c_smbus_xfer_emulated()
will happily write past the end of the supplied data buffer, thus
causing Bad Things to happen.  To prevent this, check the size
before copying the data block and return an error if it is too large.

Fixes: 209d27c3b1 ("i2c: Emulate SMBus block read over I2C")
Signed-off-by: Mans Rullgard <mans@mansr.com>
[wsa: use better errno]
Signed-off-by: Wolfram Sang <wsa@kernel.org>
This commit is contained in:
Mans Rullgard 2020-06-13 11:41:09 +01:00 committed by Wolfram Sang
parent 502035e284
commit 40e0520059
1 changed files with 7 additions and 0 deletions
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7
drivers/i2c/i2c-core-smbus.c
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@ -495,6 +495,13 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
break;
case I2C_SMBUS_BLOCK_DATA:
case I2C_SMBUS_BLOCK_PROC_CALL:
if (msg[1].buf[0] > I2C_SMBUS_BLOCK_MAX) {
dev_err(&adapter->dev,
"Invalid block size returned: %d\n",
msg[1].buf[0]);
status = -EPROTO;
goto cleanup;
}
for (i = 0; i < msg[1].buf[0] + 1; i++)
data->block[i] = msg[1].buf[i];
break;