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Petersen" , target-devel@vger.kernel.org, Mike Christie , Bart Van Assche Cc: Damien Le Moal Subject: [PATCH] tcmu: avoid use-after-free after command timeout Date: Sat, 10 Aug 2019 14:19:03 -0700 Message-Id: <20190810211903.6572-1-dmitry.fomichev@wdc.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In tcmu_handle_completion() function, the variable called read_len is always initialized with a value taken from se_cmd structure. If this function is called to complete an expired (timed out) out command, the session command pointed by se_cmd is likely to be already deallocated by the target core at that moment. As the result, this access triggers a use-after-free warning from KASAN. This patch fixes the code not to touch se_cmd when completing timed out TCMU commands. It also resets the pointer to se_cmd at the time when the TCMU_CMD_BIT_EXPIRED flag is set because it is going to become invalid after calling target_complete_cmd() later in the same function, tcmu_check_expired_cmd(). Signed-off-by: Dmitry Fomichev --- drivers/target/target_core_user.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c index 04eda111920e..a0231491fa36 100644 --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -1132,14 +1132,16 @@ static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry * struct se_cmd *se_cmd = cmd->se_cmd; struct tcmu_dev *udev = cmd->tcmu_dev; bool read_len_valid = false; - uint32_t read_len = se_cmd->data_length; + uint32_t read_len; /* * cmd has been completed already from timeout, just reclaim * data area space and free cmd */ - if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) + if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) { + WARN_ON_ONCE(se_cmd); goto out; + } list_del_init(&cmd->queue_entry); @@ -1152,6 +1154,7 @@ static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry * goto done; } + read_len = se_cmd->data_length; if (se_cmd->data_direction == DMA_FROM_DEVICE && (entry->hdr.uflags & TCMU_UFLAG_READ_LEN) && entry->rsp.read_len) { read_len_valid = true; @@ -1307,6 +1310,7 @@ static int tcmu_check_expired_cmd(int id, void *p, void *data) */ scsi_status = SAM_STAT_CHECK_CONDITION; list_del_init(&cmd->queue_entry); + cmd->se_cmd = NULL; } else { list_del_init(&cmd->queue_entry); idr_remove(&udev->commands, id);