4.14-stable review patch. If anyone has any objections, please let me know.
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From: Lin Ma linma@zju.edu.cn
[ Upstream commit ce51c817008450ef4188471db31639d42d37a5e1 ]
The functions iscsi_if_set_param() and iscsi_if_set_host_param() convert an nlattr payload to type char* and then call C string handling functions like sscanf and kstrdup:
char *data = (char*)ev + sizeof(*ev); ... sscanf(data, "%d", &value);
However, since the nlattr is provided by the user-space program and the nlmsg skb is allocated with GFP_KERNEL instead of GFP_ZERO flag (see netlink_alloc_large_skb() in netlink_sendmsg()), dirty data on the heap can lead to an OOB access for those string handling functions.
By investigating how the bug is introduced, we find it is really interesting as the old version parsing code starting from commit fd7255f51a13 ("[SCSI] iscsi: add sysfs attrs for uspace sync up") treated the nlattr as integer bytes instead of string and had length check in iscsi_copy_param():
if (ev->u.set_param.len != sizeof(uint32_t)) BUG();
But, since the commit a54a52caad4b ("[SCSI] iscsi: fixup set/get param functions"), the code treated the nlattr as C string while forgetting to add any strlen checks(), opening the possibility of an OOB access.
Fix the potential OOB by adding the strlen() check before accessing the buf. If the data passes this check, all low-level set_param handlers can safely treat this buf as legal C string.
Fixes: fd7255f51a13 ("[SCSI] iscsi: add sysfs attrs for uspace sync up") Fixes: 1d9bf13a9cf9 ("[SCSI] iscsi class: add iscsi host set param event") Signed-off-by: Lin Ma linma@zju.edu.cn Link: https://lore.kernel.org/r/20230723075820.3713119-1-linma@zju.edu.cn Reviewed-by: Chris Leech cleech@redhat.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/scsi_transport_iscsi.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c index 26c6f1b288013..d90fdfbb69de6 100644 --- a/drivers/scsi/scsi_transport_iscsi.c +++ b/drivers/scsi/scsi_transport_iscsi.c @@ -2765,6 +2765,10 @@ iscsi_set_param(struct iscsi_transport *transport, struct iscsi_uevent *ev) if (!conn || !session) return -EINVAL;
+ /* data will be regarded as NULL-ended string, do length check */ + if (strlen(data) > ev->u.set_param.len) + return -EINVAL; + switch (ev->u.set_param.param) { case ISCSI_PARAM_SESS_RECOVERY_TMO: sscanf(data, "%d", &value); @@ -2917,6 +2921,10 @@ iscsi_set_host_param(struct iscsi_transport *transport, return -ENODEV; }
+ /* see similar check in iscsi_if_set_param() */ + if (strlen(data) > ev->u.set_host_param.len) + return -EINVAL; + err = transport->set_host_param(shost, ev->u.set_host_param.param, data, ev->u.set_host_param.len); scsi_host_put(shost);