On Fri, Jun 4, 2021 at 9:17 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Jun 03, 2021 at 06:41:20AM +0000, Zheyu Ma wrote: > > In function 'neo_intr', the driver uses 'ch->ch_equeue' and > > 'ch->ch_reuque'. These two pointers are initialized in 'jsm_tty_open', > > but the interrupt handler 'neo_intr' has been registered in the probe > > progress. If 'jsm_tty_open' has not been called at this time, it will > > cause null pointer dereference. > > > > Once the driver registers the interrupt handler, the driver should be > > ready to handle it. > > > > Fix this by checking whether it is a null pointer. > > > > This log reveals it: > > > > [ 50.934983] BUG: kernel NULL pointer dereference, address: > > 0000000000000000 > > [ 50.938297] #PF: supervisor write access in kernel mode > > [ 50.940075] #PF: error_code(0x0002) - not-present page > > [ 50.940460] PGD 0 P4D 0 > > [ 50.940654] Oops: 0002 [#1] PREEMPT SMP PTI > > [ 50.940967] CPU: 2 PID: 0 Comm: swapper/2 Not tainted > > 5.12.4-g70e7f0549188-dirty #97 > > [ 50.941554] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), > > BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 > > [ 50.942419] RIP: 0010:memcpy_fromio+0x75/0xa0 > > [ 50.942759] Code: e9 02 f3 a5 41 f6 c5 02 74 02 66 a5 41 f6 c5 01 74 > > 01 a4 e8 5d 93 6b ff 5b 41 5c 41 5d 5d c3 e8 51 93 6b ff 4c 89 e7 48 89 > > de <a4> 49 89 fc 48 89 f3 49 83 ed 01 eb a4 e8 39 93 6b ff 4c 89 e7 48 > > [ 50.944158] RSP: 0018:ffffc90000118df8 EFLAGS: 00010046 > > [ 50.944559] RAX: ffff888100258000 RBX: ffffc90007f0030f > > RCX: 0000000000000000 > > [ 50.945114] RDX: 0000000000000000 RSI: ffffc90007f0030f > > RDI: 0000000000000000 > > [ 50.945652] RBP: ffffc90000118e10 R08: 0000000000000000 > > R09: 0000000000000000 > > [ 50.946192] R10: 0000000000000000 R11: 0000000000000001 > > R12: 0000000000000000 > > [ 50.946729] R13: 0000000000000001 R14: 0000000007f0021e > > R15: 0000000000000000 > > [ 50.947279] FS: 0000000000000000(0000) GS:ffff88817bc80000(0000) > > knlGS:0000000000000000 > > [ 50.947912] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 50.948346] CR2: 0000000000000000 CR3: 0000000107950000 > > CR4: 00000000000006e0 > > [ 50.948892] DR0: 0000000000000000 DR1: 0000000000000000 > > DR2: 0000000000000000 > > [ 50.949429] DR3: 0000000000000000 DR6: 00000000fffe0ff0 > > DR7: 0000000000000400 > > [ 50.949950] Call Trace: > > [ 50.950138] <IRQ> > > [ 50.950292] neo_copy_data_from_uart_to_queue+0x2f7/0x4e0 > > [ 50.950694] neo_intr+0x253/0x7a0 > > [ 50.950975] __handle_irq_event_percpu+0x53/0x3e0 > > [ 50.951352] handle_irq_event_percpu+0x35/0x90 > > [ 50.951706] handle_irq_event+0x39/0x60 > > [ 50.951999] handle_fasteoi_irq+0xc2/0x1d0 > > [ 50.952319] __common_interrupt+0x7f/0x150 > > [ 50.952638] common_interrupt+0xb4/0xd0 > > [ 50.952954] </IRQ> > > [ 50.953136] asm_common_interrupt+0x1e/0x40 > > [ 50.969513] Kernel panic - not syncing: Fatal exception in interrupt > > [ 50.970151] Dumping ftrace buffer: > > [ 50.970420] (ftrace buffer empty) > > [ 50.970693] Kernel Offset: disabled > > [ 50.970968] Rebooting in 1 seconds.. > > > > Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx> > > --- > > drivers/tty/serial/jsm/jsm_neo.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/tty/serial/jsm/jsm_neo.c b/drivers/tty/serial/jsm/jsm_neo.c > > index bf0e2a4cb0ce..46be0b53ab42 100644 > > --- a/drivers/tty/serial/jsm/jsm_neo.c > > +++ b/drivers/tty/serial/jsm/jsm_neo.c > > @@ -716,7 +716,7 @@ static void neo_parse_isr(struct jsm_board *brd, u32 port) > > return; > > > > ch = brd->channels[port]; > > - if (!ch) > > + if (!ch || !ch->ch_equeue || !ch->ch_rqueue) > > return; > > Why not just allocate the memory at probe time and not at open time? > That would resolve this issue, and probably any other problems that are > only caused by initializing things at open time. > > Once the interrupt is registered, it HAS to be able to be called, > otherwise it is a driver bug. This change keeps that broken logic still > happening and just papers over the obvious crash. > > Can you fix this the correct way instead please? > > thanks, > > greg k-h Thanks for your review, I have sent the second version of the patch. Best regards, Zheyu Ma
