On Sat, May 05, 2018 at 07:57:10AM -0500, Wenwen Wang wrote: > In i2c_smbus_xfer_emulated(), there are two buffers: msgbuf0 and msgbuf1, > which are used to save a series of messages, as mentioned in the comment. > According to the value of the variable 'size', msgbuf0 is initialized to > various values. In contrast, msgbuf1 is left uninitialized until the > function i2c_transfer() is invoked. However, msgbuf1 is not always > initialized on all possible execution paths (implementation) of > i2c_transfer(). Thus, it is possible that msgbuf1 may still be > uninitialized even after the invocation of the function i2c_transfer(), > especially when the return value of ic2_transfer() is not checked properly. > In the following execution, the uninitialized msgbuf1 will be used, such as > for security checks. Since uninitialized values can be random and > arbitrary, this will cause undefined behaviors or even check bypass. For > example, it is expected that if the value of 'size' is > I2C_SMBUS_BLOCK_PROC_CALL, the value of data->block[0] should not be larger > than I2C_SMBUS_BLOCK_MAX. But, at the end of i2c_smbus_xfer_emulated(), the > value read from msgbuf1 is assigned to data->block[0], which can > potentially lead to invalid block write size, as demonstrated in the error > message. > > This patch initializes the first byte of msgbuf1 with 0 to avoid such > undefined behaviors or security issues. > > Signed-off-by: Wenwen Wang <wang6495@xxxxxxx> From what I can tell, this patch is not needed anymore after patch 2 is applied. Correct?
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