Re: [PATCH] GenWQE: Fix bad page access during abort of resource allocation

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Oct 19, 2016 at 12:29:41PM +0200, Frank Haverkamp wrote:
> From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> 
> When interrupting an application which was allocating DMAable
> memory, it was possible, that the DMA memory was deallocated
> twice, leading to the error symptoms below.
> 
> Thanks to Gerald, who analyzed the problem and provided this
> patch.
> 
> I agree with his analysis of the problem: ddcb_cmd_fixups() ->
> genwqe_alloc_sync_sgl() (fails in f/lpage, but sgl->sgl != NULL
> and f/lpage maybe also != NULL) -> ddcb_cmd_cleanup() ->
> genwqe_free_sync_sgl() (double free, because sgl->sgl != NULL and
> f/lpage maybe also != NULL)
> 
> In this scenario we would have exactly the kind of double free that
> would explain the WARNING / Bad page state, and as expected it is
> caused by broken error handling (cleanup).
> 
> Using the Ubuntu git source, tag Ubuntu-4.4.0-33.52, he was able to reproduce
> the "Bad page state" issue, and with the patch on top he could not reproduce
> it any more.
> 
> ------------[ cut here ]------------
> WARNING: at /build/linux-o03cxz/linux-4.4.0/arch/s390/include/asm/pci_dma.h:141
> Modules linked in: qeth_l2 ghash_s390 prng aes_s390 des_s390 des_generic sha512_s390 sha256_s390 sha1_s390 sha_common genwqe_card qeth crc_itu_t qdio ccwgroup vmur dm_multipath dasd_eckd_mod dasd_mod
> CPU: 2 PID: 3293 Comm: genwqe_gunzip Not tainted 4.4.0-33-generic #52-Ubuntu
> task: 0000000032c7e270 ti: 00000000324e4000 task.ti: 00000000324e4000
> Krnl PSW : 0404c00180000000 0000000000156346 (dma_update_cpu_trans+0x9e/0xa8)
>            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 EA:3
> Krnl GPRS: 00000000324e7bcd 0000000000c3c34a 0000000027628298 000000003215b400
>            0000000000000400 0000000000001fff 0000000000000400 0000000116853000
>            07000000324e7b1e 0000000000000001 0000000000000001 0000000000000001
>            0000000000001000 0000000116854000 0000000000156402 00000000324e7a38
> Krnl Code: 000000000015633a: 95001000           cli     0(%r1),0
>            000000000015633e: a774ffc3           brc     7,1562c4
>           #0000000000156342: a7f40001           brc     15,156344
>           >0000000000156346: 92011000           mvi     0(%r1),1
>            000000000015634a: a7f4ffbd           brc     15,1562c4
>            000000000015634e: 0707               bcr     0,%r7
>            0000000000156350: c00400000000       brcl    0,156350
>            0000000000156356: eb7ff0500024       stmg    %r7,%r15,80(%r15)
> Call Trace:
> ([<00000000001563e0>] dma_update_trans+0x90/0x228)
>  [<00000000001565dc>] s390_dma_unmap_pages+0x64/0x160
>  [<00000000001567c2>] s390_dma_free+0x62/0x98
>  [<000003ff801310ce>] __genwqe_free_consistent+0x56/0x70 [genwqe_card]
>  [<000003ff801316d0>] genwqe_free_sync_sgl+0xf8/0x160 [genwqe_card]
>  [<000003ff8012bd6e>] ddcb_cmd_cleanup+0x86/0xa8 [genwqe_card]
>  [<000003ff8012c1c0>] do_execute_ddcb+0x110/0x348 [genwqe_card]
>  [<000003ff8012c914>] genwqe_ioctl+0x51c/0xc20 [genwqe_card]
>  [<000000000032513a>] do_vfs_ioctl+0x3b2/0x518
>  [<0000000000325344>] SyS_ioctl+0xa4/0xb8
>  [<00000000007b86c6>] system_call+0xd6/0x264
>  [<000003ff9e8e520a>] 0x3ff9e8e520a
> Last Breaking-Event-Address:
>  [<0000000000156342>] dma_update_cpu_trans+0x9a/0xa8
> ---[ end trace 35996336235145c8 ]---
> BUG: Bad page state in process jbd2/dasdb1-8  pfn:3215b
> page:000003d100c856c0 count:-1 mapcount:0 mapping:          (null) index:0x0
> flags: 0x3fffc0000000000()
> page dumped because: nonzero _count
> 
> Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com>

As you say this goes back to at least 4.4, shouldn't we mark it for
stable releases?  And if so, any idea how far back it goes?

thanks,

greg k-h