[SRU][Q:linux-azure][PATCH 4/4] net: mana: fix use-after-free in mana_hwc_destroy_channel() by reordering teardown

[John Cabaj]

From: Dipayaan Roy <dipayanroy at linux.microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/2146588

A potential race condition exists in mana_hwc_destroy_channel() where
hwc->caller_ctx is freed before the HWC's Completion Queue (CQ) and
Event Queue (EQ) are destroyed. This allows an in-flight CQ interrupt
handler to dereference freed memory, leading to a use-after-free or
NULL pointer dereference in mana_hwc_handle_resp().

mana_smc_teardown_hwc() signals the hardware to stop but does not
synchronize against IRQ handlers already executing on other CPUs. The
IRQ synchronization only happens in mana_hwc_destroy_cq() via
mana_gd_destroy_eq() -> mana_gd_deregister_irq(). Since this runs
after kfree(hwc->caller_ctx), a concurrent mana_hwc_rx_event_handler()
can dereference freed caller_ctx (and rxq->msg_buf) in
mana_hwc_handle_resp().

Fix this by reordering teardown to reverse-of-creation order: destroy
the TX/RX work queues and CQ/EQ before freeing hwc->caller_ctx. This
ensures all in-flight interrupt handlers complete before the memory they
access is freed.

Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Reviewed-by: Haiyang Zhang <haiyangz at microsoft.com>
Signed-off-by: Dipayaan Roy <dipayanroy at linux.microsoft.com>
Reviewed-by: Simon Horman <horms at kernel.org>
Link: https://patch.msgid.link/abHA3AjNtqa1nx9k@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(cherry picked from commit fa103fc8f56954a60699a29215cb713448a39e87)
Signed-off-by: John Cabaj <john.cabaj at canonical.com>
---
 drivers/net/ethernet/microsoft/mana/hw_channel.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c b/drivers/net/ethernet/microsoft/mana/hw_channel.c
index aa4e2731e2ba..840c6b8957c9 100644
--- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
+++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
@@ -814,9 +814,6 @@ void mana_hwc_destroy_channel(struct gdma_context *gc)
 		gc->max_num_cqs = 0;
 	}
 
-	kfree(hwc->caller_ctx);
-	hwc->caller_ctx = NULL;
-
 	if (hwc->txq)
 		mana_hwc_destroy_wq(hwc, hwc->txq);
 
@@ -826,6 +823,9 @@ void mana_hwc_destroy_channel(struct gdma_context *gc)
 	if (hwc->cq)
 		mana_hwc_destroy_cq(hwc->gdma_dev->gdma_context, hwc->cq);
 
+	kfree(hwc->caller_ctx);
+	hwc->caller_ctx = NULL;
+
 	mana_gd_free_res_map(&hwc->inflight_msg_res);
 
 	hwc->num_inflight_msg = 0;
-- 
2.43.0