Re: [2.6.23 PATCH 07/18] dm io: fix panic on large request

[Patrick McHardy <kaber@trash.net>]

Alasdair G Kergon wrote:
> From: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>
> 
> bio_alloc_bioset() will return NULL if 'num_vecs' is too large.
> Use bio_get_nr_vecs() to get estimation of maximum number.
> 
> Signed-off-by: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>
> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
> 
> ---
>  drivers/md/dm-io.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletion(-)


This patch reproducibly oopses my box:

[  126.754204] BUG: unable to handle kernel NULL pointer dereference at
virtual address 00000000
[  126.754326]  printing eip:
[  126.754369] c0141a67
[  126.754420] *pde = 00000000
[  126.754465] Oops: 0000 [#1]
[  126.754507] PREEMPT
[  126.754585] Modules linked in: [...]


[  126.758372] CPU:    0
[  126.758373] EIP:    0060:[<c0141a67>]    Not tainted VLI
[  126.758374] EFLAGS: 00010282   (2.6.22 #1)
[  126.758511] EIP is at mempool_free+0xe/0xc0
[  126.758558] eax: d39e65d0   ebx: 00000000   ecx: df2b9898   edx: 00000000
[  126.758605] esi: 00000000   edi: d39e65d0   ebp: d487d6d0   esp: df79fec0
[  126.758652] ds: 007b   es: 007b   fs: 0000  gs: 0000  ss: 0068
[  126.758699] Process kcryptd/0 (pid: 3218, ti=df79f000 task=df2b9640
task.ti=df79f000)
[  126.758747] Stack: 00000000 00000000 d3835f80 00000000 e08b0923
e08a5f69 00000200 e0ad1080
[  126.759093]        dfb5ab40 d3835f80 e08b08c0 00000000 e08a5fb7
c01804d8 00000000 00000200
[  126.759439]        c520bc00 00000c00 d0b77438 d5754b00 df79ff5c
e08a515e d0b77444 d5754b00
[  126.759858] Call Trace:
[  126.759965]  [<e08b0923>] clone_endio+0x63/0xc0 [dm_mod]
[  126.760066]  [<e08a5f69>] crypt_convert+0x131/0x17f [dm_crypt]
[  126.760168]  [<e08b08c0>] clone_endio+0x0/0xc0 [dm_mod]
[  126.760264]  [<e08a5fb7>] kcryptd_do_work+0x0/0x30f [dm_crypt]
[  126.760349]  [<c01804d8>] bio_endio+0x33/0x5d
[  126.760462]  [<e08a515e>] dec_pending+0x28/0x39 [dm_crypt]
[  126.760558]  [<e08a61e6>] kcryptd_do_work+0x22f/0x30f [dm_crypt]
[  126.760669]  [<c0112182>] update_stats_wait_end+0x7f/0xb2
[  126.760801]  [<e08a5fb7>] kcryptd_do_work+0x0/0x30f [dm_crypt]
[  126.760888]  [<c012700e>] run_workqueue+0x84/0x179
[  126.760990]  [<c0127292>] worker_thread+0x0/0xf0
[  126.761074]  [<c012732f>] worker_thread+0x9d/0xf0
[  126.761160]  [<c012a360>] autoremove_wake_function+0x0/0x37
[  126.761256]  [<c0127292>] worker_thread+0x0/0xf0
[  126.761334]  [<c012a15c>] kthread+0x52/0x58
[  126.761411]  [<c012a10a>] kthread+0x0/0x58
[  126.761496]  [<c0104983>] kernel_thread_helper+0x7/0x14
[  126.761598]  =======================
[  126.761717] Code: 1c 00 89 f6 eb a9 b8 88 13 00 00 e8 b4 56 1c 00 8d
74 26 00 eb d5 31 db e9 11 ff ff ff 57 56 53 83 ec 04 89 c7 89 d6 85 c0
74 55 <8b> 02 39 42 04 7d 46 9c 58 90 8d b4 26 00 00 00 00 89 c3 fa 90
[  126.763964] EIP: [<c0141a67>] mempool_free+0xe/0xc0 SS:ESP 0068:df79fec0
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