[PATCH v2] net/mlx5e: always initialize frag->last_in_page

From: Qian Cai
Date: Thu Aug 01 2019 - 09:53:15 EST


The commit 069d11465a80 ("net/mlx5e: RX, Enhance legacy Receive Queue
memory scheme") introduced an undefined behaviour below due to
"frag->last_in_page" is only initialized in mlx5e_init_frags_partition()
when,

if (next_frag.offset + frag_info[f].frag_stride > PAGE_SIZE)

or after bailed out the loop,

for (i = 0; i < mlx5_wq_cyc_get_size(&rq->wqe.wq); i++)

As the result, there could be some "frag" have uninitialized
value of "last_in_page".

Later, get_frag() obtains those "frag" and check "frag->last_in_page" in
mlx5e_put_rx_frag() and triggers the error during boot. Fix it by always
initializing "frag->last_in_page" to "false" in
mlx5e_init_frags_partition().

UBSAN: Undefined behaviour in
drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:325:12
load of value 170 is not a valid value for type 'bool' (aka '_Bool')
Call trace:
dump_backtrace+0x0/0x264
show_stack+0x20/0x2c
dump_stack+0xb0/0x104
__ubsan_handle_load_invalid_value+0x104/0x128
mlx5e_handle_rx_cqe+0x8e8/0x12cc [mlx5_core]
mlx5e_poll_rx_cq+0xca8/0x1a94 [mlx5_core]
mlx5e_napi_poll+0x17c/0xa30 [mlx5_core]
net_rx_action+0x248/0x940
__do_softirq+0x350/0x7b8
irq_exit+0x200/0x26c
__handle_domain_irq+0xc8/0x128
gic_handle_irq+0x138/0x228
el1_irq+0xb8/0x140
arch_cpu_idle+0x1a4/0x348
do_idle+0x114/0x1b0
cpu_startup_entry+0x24/0x28
rest_init+0x1ac/0x1dc
arch_call_rest_init+0x10/0x18
start_kernel+0x4d4/0x57c

Fixes: 069d11465a80 ("net/mlx5e: RX, Enhance legacy Receive Queue memory scheme")
Signed-off-by: Qian Cai <cai@xxxxxx>
---

v2: zero-init the whole struct instead per Tariq.

drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 47eea6b3a1c3..e1810c03a510 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -331,12 +331,11 @@ static inline u64 mlx5e_get_mpwqe_offset(struct mlx5e_rq *rq, u16 wqe_ix)

static void mlx5e_init_frags_partition(struct mlx5e_rq *rq)
{
- struct mlx5e_wqe_frag_info next_frag, *prev;
+ struct mlx5e_wqe_frag_info next_frag = {};
+ struct mlx5e_wqe_frag_info *prev = NULL;
int i;

next_frag.di = &rq->wqe.di[0];
- next_frag.offset = 0;
- prev = NULL;

for (i = 0; i < mlx5_wq_cyc_get_size(&rq->wqe.wq); i++) {
struct mlx5e_rq_frag_info *frag_info = &rq->wqe.info.arr[0];
--
1.8.3.1