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Krzysztof Kozlowski authored
Interrupt handler processes multiple message write requests one after another, till the driver message queue is drained. However if driver encounters a read message without preceding START, it stops the I2C transfer as it is an invalid condition for the controller. At least the comment describes a requirement "the controller forces us to send a new START when we change direction". This stop results in clearing the message queue (i2c->msg = NULL). The code however immediately jumped back to label "retry_write" which dereferenced the "i2c->msg" making it a possible NULL pointer dereference. The Coverity analysis: 1. Condition !is_msgend(i2c), taking false branch. if (!is_msgend(i2c)) { 2. Condition !is_lastmsg(i2c), taking true branch. } else if (!is_lastmsg(i2c)) { 3. Condition i2c->msg->flags & 1, taking true branch. if (i2c->msg->flags & I2C_M_RD) { 4. write_zero_model: Passing i2c to s3c24xx_i2c_stop, which sets i2c->msg to NULL. s3c24xx_i2c_stop(i2c, -EINVAL); 5. Jumping to label retry_write. goto retry_write; 6. var_deref_model: Passing i2c to is_msgend, which dereferences null i2c->msg. if (!is_msgend(i2c)) {" All previous calls to s3c24xx_i2c_stop() in this interrupt service routine are followed by jumping to end of function (acknowledging the interrupt and returning). This seems a reasonable choice also here since message buffer was entirely emptied. Addresses-Coverity: Explicit null dereferenced Fixes: 1da177e4 ("Linux-2.6.12-rc2") Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> Signed-off-by: Wolfram Sang <wsa@kernel.org>
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