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From: Stefani Seibold on 13 Aug 2010 16:50

The scatterlist is used uninitialized in kfifo_dma_in_prepare(). This
triggers the following bug if CONFIG_DEBUG_SG=y:

------------[ cut here ]------------
kernel BUG at include/linux/scatterlist.h:65!
invalid opcode: 0000 [#1] PREEMPT SMP
...
Call Trace:
[<ffffffff810a1eab>] setup_sgl+0x6b/0xe0
[<ffffffffa03d7000>] ? example_init+0x0/0x265 [dma_example]
[<ffffffff810a2021>] __kfifo_dma_in_prepare+0x21/0x30
[<ffffffffa03d7124>] example_init+0x124/0x265 [dma_example]
[<ffffffff810f9c55>] ? trace_module_notify+0x25/0x370
[<ffffffff81110c6e>] ? free_pages_prepare+0x11e/0x1e0
[<ffffffff8106f2b1>] ? get_parent_ip+0x11/0x50
[<ffffffff810f9c55>] ? trace_module_notify+0x25/0x370
[<ffffffff810b65fd>] ? trace_hardirqs_on+0xd/0x10
[<ffffffff814beade>] ? mutex_unlock+0xe/0x10
[<ffffffff810f9c71>] ? trace_module_notify+0x41/0x370
[<ffffffff810a77d5>] ? __blocking_notifier_call_chain+0x45/0x80
[<ffffffff81137b7a>] ? vfree+0x2a/0x30
[<ffffffff810a6ac3>] ? up_read+0x23/0x40
[<ffffffff810a77f5>] ? __blocking_notifier_call_chain+0x65/0x80
[<ffffffff810001e3>] do_one_initcall+0x43/0x180
[<ffffffff810c577a>] sys_init_module+0xba/0x200
[<ffffffff8103819b>] system_call_fastpath+0x16/0x1b
RIP [<ffffffff810a1e31>] setup_sgl_buf+0x1a1/0x1b0
RSP <ffff88006720dc98>
---[ end trace a72b979fd3c1d3a5 ]---

Add the proper initialization to avoid the bug.

Signed-off-by: Andrea Righi <arighi(a)develer.com>
Acked-by: Stefani Seibold <stefani(a)seibold.net>
---
samples/kfifo/dma-example.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/samples/kfifo/dma-example.c b/samples/kfifo/dma-example.c
index b9482c2..03433ca 100644
--- a/samples/kfifo/dma-example.c
+++ b/samples/kfifo/dma-example.c
@@ -45,6 +45,7 @@ static int __init example_init(void)

printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));

+ sg_init_table(sg, ARRAY_SIZE(sg));
ret = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
printk(KERN_INFO "DMA sgl entries: %d\n", ret);



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Prev: kfifo: fix a memory leak in dma example
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