[PATCH] scsi: qedf: Fix a UAF bug in __qedf_probe

[Letu Ren]

In __qedf_probe, if `qedf->cdev` is NULL which means
qed_ops->common->probe() failed, then the program will goto label err1,
scsi_host_put() will free `lport->host` pointer. Because the memory `qedf`
points to is allocated by libfc_host_alloc(), it will be freed by
scsi_host_put(). However, the if statement below label err0 only checks
whether qedf is NULL but doesn't check whether the memory has been freed.
So a UAF bug occurred.

There are two ways to get to the statements below err0. the first one is
described as before. `qedf` should be set to NULL. The second way is goto
`err0` directly. In this way `qedf` hasn't been changed and it has the
initial value `NULL`. So the program wont't go to the if statement in any
situation.

The KASAN logs are as follows:

[    2.312969] BUG: KASAN: use-after-free in __qedf_probe+0x5dcf/0x6bc0
[    2.312969]
[    2.312969] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[    2.312969] Call Trace:
[    2.312969]  dump_stack_lvl+0x59/0x7b
[    2.312969]  print_address_description+0x7c/0x3b0
[    2.312969]  ? __qedf_probe+0x5dcf/0x6bc0
[    2.312969]  __kasan_report+0x160/0x1c0
[    2.312969]  ? __qedf_probe+0x5dcf/0x6bc0
[    2.312969]  kasan_report+0x4b/0x70
[    2.312969]  ? kobject_put+0x25d/0x290
[    2.312969]  kasan_check_range+0x2ca/0x310
[    2.312969]  __qedf_probe+0x5dcf/0x6bc0
[    2.312969]  ? selinux_kernfs_init_security+0xdc/0x5f0
[    2.312969]  ? trace_rpm_return_int_rcuidle+0x18/0x120
[    2.312969]  ? rpm_resume+0xa5c/0x16e0
[    2.312969]  ? qedf_get_generic_tlv_data+0x160/0x160
[    2.312969]  local_pci_probe+0x13c/0x1f0
[    2.312969]  pci_device_probe+0x37e/0x6c0

Reported-by: Zheyu Ma <zheyuma97@xxxxxxxxx>
Signed-off-by: Letu Ren <fantasquex@xxxxxxxxx>
Co-developed-by: Wende Tan <twd2.me@xxxxxxxxx>
Signed-off-by: Wende Tan <twd2.me@xxxxxxxxx>
---
 drivers/scsi/qedf/qedf_main.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/scsi/qedf/qedf_main.c b/drivers/scsi/qedf/qedf_main.c
index 42d0d941dba5..3ea552acd82a 100644
--- a/drivers/scsi/qedf/qedf_main.c
+++ b/drivers/scsi/qedf/qedf_main.c
@@ -3683,11 +3683,6 @@ static int __qedf_probe(struct pci_dev *pdev, int mode)
 err1:
 	scsi_host_put(lport->host);
 err0:
-	if (qedf) {
-		QEDF_INFO(&qedf->dbg_ctx, QEDF_LOG_DISC, "Probe done.\n");
-
-		clear_bit(QEDF_PROBING, &qedf->flags);
-	}
 	return rc;
 }
 
-- 
2.33.1