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author | Samir Virmani <samir@embedur.com> | 2019-01-16 10:28:07 -0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-01-18 13:03:47 +0100 |
commit | aff9cf5955185d1f183227e46c5f8673fa483813 (patch) | |
tree | a689db3fa95f6ef74361c4ef4851e1e626d4eed9 /drivers/tty/serial/serial_core.c | |
parent | 1c7fc5cbc33980acd13d668f1c8f0313d6ae9fd8 (diff) | |
download | linux-stable-aff9cf5955185d1f183227e46c5f8673fa483813.tar.gz linux-stable-aff9cf5955185d1f183227e46c5f8673fa483813.tar.bz2 linux-stable-aff9cf5955185d1f183227e46c5f8673fa483813.zip |
uart: Fix crash in uart_write and uart_put_char
We were experiencing a crash similar to the one reported as part of
commit:a5ba1d95e46e ("uart: fix race between uart_put_char() and
uart_shutdown()") in our testbed as well. We continue to observe the same
crash after integrating the commit a5ba1d95e46e ("uart: fix race between
uart_put_char() and uart_shutdown()")
On reviewing the change, the port lock should be taken prior to checking for
if (!circ->buf) in fn. __uart_put_char and other fns. that update the buffer
uart_state->xmit.
Traceback:
[11/27/2018 06:24:32.4870] Unable to handle kernel NULL pointer dereference
at virtual address 0000003b
[11/27/2018 06:24:32.4950] PC is at memcpy+0x48/0x180
[11/27/2018 06:24:32.4950] LR is at uart_write+0x74/0x120
[11/27/2018 06:24:32.4950] pc : [<ffffffc0002e6808>]
lr : [<ffffffc0003747cc>] pstate: 000001c5
[11/27/2018 06:24:32.4950] sp : ffffffc076433d30
[11/27/2018 06:24:32.4950] x29: ffffffc076433d30 x28: 0000000000000140
[11/27/2018 06:24:32.4950] x27: ffffffc0009b9d5e x26: ffffffc07ce36580
[11/27/2018 06:24:32.4950] x25: 0000000000000000 x24: 0000000000000140
[11/27/2018 06:24:32.4950] x23: ffffffc000891200 x22: ffffffc01fc34000
[11/27/2018 06:24:32.4950] x21: 0000000000000fff x20: 0000000000000076
[11/27/2018 06:24:32.4950] x19: 0000000000000076 x18: 0000000000000000
[11/27/2018 06:24:32.4950] x17: 000000000047cf08 x16: ffffffc000099e68
[11/27/2018 06:24:32.4950] x15: 0000000000000018 x14: 776d726966205948
[11/27/2018 06:24:32.4950] x13: 50203a6c6974755f x12: 74647075205d3333
[11/27/2018 06:24:32.4950] x11: 3a35323a36203831 x10: 30322f37322f3131
[11/27/2018 06:24:32.4950] x9 : 5b205d303638342e x8 : 746164206f742070
[11/27/2018 06:24:32.4950] x7 : 7520736920657261 x6 : 000000000000003b
[11/27/2018 06:24:32.4950] x5 : 000000000000817a x4 : 0000000000000008
[11/27/2018 06:24:32.4950] x3 : 2f37322f31312a5b x2 : 000000000000006e
[11/27/2018 06:24:32.4950] x1 : ffffffc0009b9cf0 x0 : 000000000000003b
[11/27/2018 06:24:32.4950] CPU2: stopping
[11/27/2018 06:24:32.4950] CPU: 2 PID: 0 Comm: swapper/2 Tainted: P D O 4.1.51 #3
[11/27/2018 06:24:32.4950] Hardware name: Broadcom-v8A (DT)
[11/27/2018 06:24:32.4950] Call trace:
[11/27/2018 06:24:32.4950] [<ffffffc0000883b8>] dump_backtrace+0x0/0x150
[11/27/2018 06:24:32.4950] [<ffffffc00008851c>] show_stack+0x14/0x20
[11/27/2018 06:24:32.4950] [<ffffffc0005ee810>] dump_stack+0x90/0xb0
[11/27/2018 06:24:32.4950] [<ffffffc00008e844>] handle_IPI+0x18c/0x1a0
[11/27/2018 06:24:32.4950] [<ffffffc000080c68>] gic_handle_irq+0x88/0x90
Fixes: a5ba1d95e46e ("uart: fix race between uart_put_char() and uart_shutdown()")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Samir Virmani <samir@embedur.com>
Acked-by: Tycho Andersen <tycho@tycho.ws>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial/serial_core.c')
-rw-r--r-- | drivers/tty/serial/serial_core.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index d4cca5bdaf1c..5c01bb6d1c24 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -550,10 +550,12 @@ static int uart_put_char(struct tty_struct *tty, unsigned char c) int ret = 0; circ = &state->xmit; - if (!circ->buf) + port = uart_port_lock(state, flags); + if (!circ->buf) { + uart_port_unlock(port, flags); return 0; + } - port = uart_port_lock(state, flags); if (port && uart_circ_chars_free(circ) != 0) { circ->buf[circ->head] = c; circ->head = (circ->head + 1) & (UART_XMIT_SIZE - 1); @@ -586,11 +588,13 @@ static int uart_write(struct tty_struct *tty, return -EL3HLT; } + port = uart_port_lock(state, flags); circ = &state->xmit; - if (!circ->buf) + if (!circ->buf) { + uart_port_unlock(port, flags); return 0; + } - port = uart_port_lock(state, flags); while (port) { c = CIRC_SPACE_TO_END(circ->head, circ->tail, UART_XMIT_SIZE); if (count < c) |