[PATCH v11] net/bnx2x: Prevent access to a freed page in page_pool

[Thinh Tran <thinhtr@linux.ibm.com>]

Fix race condition leading to system crash during EEH error handling

During EEH error recovery, the bnx2x driver's transmit timeout logic
could cause a race condition when handling reset tasks. The
bnx2x_tx_timeout() schedules reset tasks via bnx2x_sp_rtnl_task(),
which ultimately leads to bnx2x_nic_unload(). In bnx2x_nic_unload()
SGEs are freed using bnx2x_free_rx_sge_range(). However, this could
overlap with the EEH driver's attempt to reset the device using
bnx2x_io_slot_reset(), which also tries to free SGEs. This race 
condition can result in system crashes due to accessing freed memory
locations in bnx2x_free_rx_sge()

799  static inline void bnx2x_free_rx_sge(struct bnx2x *bp,
800				struct bnx2x_fastpath *fp, u16 index)
801  {
802	struct sw_rx_page *sw_buf = &fp->rx_page_ring[index];
803     struct page *page = sw_buf->page;
....
where sw_buf was set to NULL after the call to dma_unmap_page() 
by the preceding thread.


[  793.003930] EEH: Beginning: 'slot_reset'
[  793.003937] PCI 0011:01:00.0#10000: EEH: Invoking bnx2x->slot_reset()
[  793.003939] bnx2x: [bnx2x_io_slot_reset:14228(eth1)]IO slot reset initializing...
[  793.004037] bnx2x 0011:01:00.0: enabling device (0140 -> 0142)
[  793.008839] bnx2x: [bnx2x_io_slot_reset:14244(eth1)]IO slot reset --> driver unload
[  793.122134] Kernel attempted to read user page (0) - exploit attempt? (uid: 0)
[  793.122143] BUG: Kernel NULL pointer dereference on read at 0x00000000
[  793.122147] Faulting instruction address: 0xc0080000025065fc
[  793.122152] Oops: Kernel access of bad area, sig: 11 [#1]
.....
[  793.122315] Call Trace:
[  793.122318] [c000000003c67a20] [c00800000250658c] bnx2x_io_slot_reset+0x204/0x610 [bnx2x] (unreliable)
[  793.122331] [c000000003c67af0] [c0000000000518a8] eeh_report_reset+0xb8/0xf0
[  793.122338] [c000000003c67b60] [c000000000052130] eeh_pe_report+0x180/0x550
[  793.122342] [c000000003c67c70] [c00000000005318c] eeh_handle_normal_event+0x84c/0xa60
[  793.122347] [c000000003c67d50] [c000000000053a84] eeh_event_handler+0xf4/0x170
[  793.122352] [c000000003c67da0] [c000000000194c58] kthread+0x1c8/0x1d0
[  793.122356] [c000000003c67e10] [c00000000000cf64] ret_from_kernel_thread+0x5c/0x64

To solve this issue, we need to verify page pool allocations before
freeing.

Fixes: 4cace675d687 ("bnx2x: Alloc 4k fragment for each rx ring buffer element")

Signed-off-by: Thinh Tran <thinhtr@linux.ibm.com>

---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h
index d8b1824c334d..0bc1367fd649 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h
@@ -1002,9 +1002,6 @@ static inline void bnx2x_set_fw_mac_addr(__le16 *fw_hi, __le16 *fw_mid,
 static inline void bnx2x_free_rx_mem_pool(struct bnx2x *bp,
 					  struct bnx2x_alloc_pool *pool)
 {
-	if (!pool->page)
-		return;
-
 	put_page(pool->page);
 
 	pool->page = NULL;
@@ -1015,6 +1012,9 @@ static inline void bnx2x_free_rx_sge_range(struct bnx2x *bp,
 {
 	int i;
 
+	if (!fp->page_pool.page)
+		return;
+
 	if (fp->mode == TPA_MODE_DISABLED)
 		return;
 
-- 
2.25.1