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authorKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>2021-05-26 08:39:37 -0400
committerWolfram Sang <wsa@kernel.org>2021-05-28 10:16:23 +0200
commit24990423267ec283b9d86f07f362b753eb9b0ed5 (patch)
tree7985b72b018925d7b0c34f8baee376377e862ca1
parentfed1bd51a504eb96caa38b4f13ab138fc169ea75 (diff)
i2c: s3c2410: fix possible NULL pointer deref on read message after write
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: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> Signed-off-by: Wolfram Sang <wsa@kernel.org>
-rw-r--r--drivers/i2c/busses/i2c-s3c2410.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index ab928613afba..4d82761e1585 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -480,7 +480,10 @@ static int i2c_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
* forces us to send a new START
* when we change direction
*/
+ dev_dbg(i2c->dev,
+ "missing START before write->read\n");
s3c24xx_i2c_stop(i2c, -EINVAL);
+ break;
}
goto retry_write;