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scsi: target: tcmu: avoid use-after-free after command timeout

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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 <dmitry.fomichev@wdc.com>
Acked-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Dmitry Fomichev 2019-08-11 11:25:10 -07:00 committed by Martin K. Petersen
parent 26fa656e9a
commit a86a75865f
1 changed files with 7 additions and 2 deletions
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9
drivers/target/target_core_user.c
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@ -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);
@ -2022,6 +2026,7 @@ static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)
idr_remove(&udev->commands, i);
if (!test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
WARN_ON(!cmd->se_cmd);
list_del_init(&cmd->queue_entry);
if (err_level == 1) {
/*