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Subject[PATCH v2] kernel/dma: Fix panic caused by passing swiotlb to command line
Date
From: He Zhe <zhe.he@windriver.com>

setup_io_tlb_npages does not check input argument before passing it
to isdigit. The argument would be a NULL pointer if "swiotlb", without
its value, is set in command line and thus causes the following panic.

PANIC: early exception 0xe3 IP 10:ffffffffbb9b8e9f error 0 cr2 0x0
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc3-yocto-standard+ #9
[ 0.000000] RIP: 0010:setup_io_tlb_npages+0xf/0x95
...
[ 0.000000] Call Trace:
[ 0.000000] do_early_param+0x57/0x8e
[ 0.000000] parse_args+0x208/0x320
[ 0.000000] ? rdinit_setup+0x30/0x30
[ 0.000000] parse_early_options+0x29/0x2d
[ 0.000000] ? rdinit_setup+0x30/0x30
[ 0.000000] parse_early_param+0x36/0x4d
[ 0.000000] setup_arch+0x336/0x99e
[ 0.000000] start_kernel+0x6f/0x4e6
[ 0.000000] x86_64_start_reservations+0x24/0x26
[ 0.000000] x86_64_start_kernel+0x6f/0x72
[ 0.000000] secondary_startup_64+0xa4/0xb0

This patch adds a check to prevent the panic and sets it for 4MB by default.

Signed-off-by: He Zhe <zhe.he@windriver.com>
Cc: stable@vger.kernel.org
Cc: konrad.wilk@oracle.com
Cc: hch@lst.de
Cc: m.szyprowski@samsung.com
Cc: robin.murphy@arm.com

Signed-off-by: He Zhe <zhe.he@windriver.com>
---
v2: Set swiotlb for 4MB by default

kernel/dma/swiotlb.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 045930e..0e18cd4 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -58,6 +58,9 @@
*/
#define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)

+#define IO_TLB_DEFAULT_MB 4
+#define IO_TLB_DEFAULT_SLABS ((IO_TLB_DEFAULT_MB<<20) >> IO_TLB_SHIFT)
+
enum swiotlb_force swiotlb_force;

/*
@@ -103,6 +106,14 @@ static int late_alloc;
static int __init
setup_io_tlb_npages(char *str)
{
+ if (!str) {
+ pr_err("No value provided for swiotlb, "
+ "set it to %d slabs for %dMB by default.\n",
+ IO_TLB_DEFAULT_SLABS, IO_TLB_DEFAULT_MB);
+ io_tlb_nslabs = IO_TLB_DEFAULT_SLABS;
+ return 0;
+ }
+
if (isdigit(*str)) {
io_tlb_nslabs = simple_strtoul(str, &str, 0);
/* avoid tail segment of size < IO_TLB_SEGSIZE */
--
2.7.4
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