From: Hector Martin marcan@marcan.st
(Hector Martin wrote) This fixes segfaults when a card gets yanked off of the PCIe bus while busy, e.g. with a userspace app trying to get the cycle time:
[8638860.994310] Call Trace: [8638860.994313] ioctl_get_cycle_timer2+0x4f/0xd0 [firewire_core] [8638860.994323] fw_device_op_ioctl+0xae/0x150 [firewire_core] [8638860.994328] __x64_sys_ioctl+0x7d/0xb0 [8638860.994332] do_syscall_64+0x45/0x80 [8638860.994337] entry_SYSCALL_64_after_hwframe+0x44/0xae
(Takashi Sakamoto wrote) As long as reading commit 20802224298c ("firewire: core: add forgotten dummy driver methods, remove unused ones"), three functions are not implemeted in dummy driver for reason; .read_csr, .write_csr, and .set_config_rom.
In core of Linux FireWire subsystem, the callback of .set_config_rom is under acquisition of mutual exclusive for local list of card. The acquision is also done in process for removal of card, therefore it's safe for missing implementation of .set_config_rom.
On the other hand, no lock primitive accompanies any call of .read_csr and .write_csr. For userspace client, check of node shutdown is done in the beginning of dispatch of ioctl request, while node shifts to shutdown state in workqueue context enough after card shifts to dummy driver. It's probable that these two functions are called for the dummy driver by the code of userspace client. In-kernel unit driver has similar situation. It's better to add implementation of the two functions for dummy driver.
Signed-off-by: Hector Martin marcan@marcan.st --- drivers/firewire/core-card.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/firewire/core-card.c b/drivers/firewire/core-card.c index 54be88167c60..d994da6cf465 100644 --- a/drivers/firewire/core-card.c +++ b/drivers/firewire/core-card.c @@ -616,6 +616,15 @@ static struct fw_iso_context *dummy_allocate_iso_context(struct fw_card *card, return ERR_PTR(-ENODEV); }
+static u32 dummy_read_csr(struct fw_card *card, int csr_offset) +{ + return 0; +} + +static void dummy_write_csr(struct fw_card *card, int csr_offset, u32 value) +{ +} + static int dummy_start_iso(struct fw_iso_context *ctx, s32 cycle, u32 sync, u32 tags) { @@ -649,6 +658,8 @@ static const struct fw_card_driver dummy_driver_template = { .send_response = dummy_send_response, .cancel_packet = dummy_cancel_packet, .enable_phys_dma = dummy_enable_phys_dma, + .read_csr = dummy_read_csr, + .write_csr = dummy_write_csr, .allocate_iso_context = dummy_allocate_iso_context, .start_iso = dummy_start_iso, .set_iso_channels = dummy_set_iso_channels,