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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Subject: [PATCH net] net: ena: fix shift-out-of-bounds in exponential backoff Message-ID: <20230711013621.GE1926@templeofstupid.com> MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The ENA adapters on our instances occasionally reset. Once recently logged a UBSAN failure to console in the process: UBSAN: shift-out-of-bounds in build/linux/drivers/net/ethernet/amazon/ena= /ena_com.c:540:13 shift exponent 32 is too large for 32-bit type 'unsigned int' CPU: 28 PID: 70012 Comm: kworker/u72:2 Kdump: loaded not tainted 5.15.117 Hardware name: Amazon EC2 c5d.9xlarge/, BIOS 1.0 10/16/2017 Workqueue: ena ena_fw_reset_device [ena] Call Trace: dump_stack_lvl+0x4a/0x63 dump_stack+0x10/0x16 ubsan_epilogue+0x9/0x36 __ubsan_handle_shift_out_of_bounds.cold+0x61/0x10e ? __const_udelay+0x43/0x50 ena_delay_exponential_backoff_us.cold+0x16/0x1e [ena] wait_for_reset_state+0x54/0xa0 [ena] ena_com_dev_reset+0xc8/0x110 [ena] ena_down+0x3fe/0x480 [ena] ena_destroy_device+0xeb/0xf0 [ena] ena_fw_reset_device+0x30/0x50 [ena] process_one_work+0x22b/0x3d0 worker_thread+0x4d/0x3f0 ? process_one_work+0x3d0/0x3d0 kthread+0x12a/0x150 ? set_kthread_struct+0x50/0x50 ret_from_fork+0x22/0x30 Apparently, the reset delays are getting so large they can trigger a UBSAN panic. Looking at the code, the current timeout is capped at 5000us. Using a base value of 100us, the current code will overflow after (1<<29). Even at values before 32, this function wraps around, perhaps unintentionally. Cap the value of the exponent used for this backoff at (1<<16) which is larger than currently necessary, but large enough to support bigger values in the future. Cc: stable@vger.kernel.org Fixes: 4bb7f4cf60e3 ("net: ena: reduce driver load time") Signed-off-by: Krister Johansen Reviewed-by: Leon Romanovsky Reviewed-by: Shay Agroskin --- drivers/net/ethernet/amazon/ena/ena_com.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c b/drivers/net/ethern= et/amazon/ena/ena_com.c index 451c3a1b6255..633b321d7fdd 100644 --- a/drivers/net/ethernet/amazon/ena/ena_com.c +++ b/drivers/net/ethernet/amazon/ena/ena_com.c @@ -35,6 +35,8 @@ =20 #define ENA_REGS_ADMIN_INTR_MASK 1 =20 +#define ENA_MAX_BACKOFF_DELAY_EXP 16U + #define ENA_MIN_ADMIN_POLL_US 100 =20 #define ENA_MAX_ADMIN_POLL_US 5000 @@ -536,6 +538,7 @@ static int ena_com_comp_status_to_errno(struct ena_com_= admin_queue *admin_queue, =20 static void ena_delay_exponential_backoff_us(u32 exp, u32 delay_us) { + exp =3D min_t(u32, exp, ENA_MAX_BACKOFF_DELAY_EXP); delay_us =3D max_t(u32, ENA_MIN_ADMIN_POLL_US, delay_us); delay_us =3D min_t(u32, delay_us * (1U << exp), ENA_MAX_ADMIN_POLL_US); usleep_range(delay_us, 2 * delay_us); --=20 2.25.1