ata: sata_dwc_460ex: Fix crash due to OOB write
commit
7aa8104a554713b685db729e66511b93d989dd6a upstream.
the driver uses libata's "tag" values from in various arrays.
Since the mentioned patch bumped the ATA_TAG_INTERNAL to 32,
the value of the SATA_DWC_QCMD_MAX needs to account for that.
Otherwise ATA_TAG_INTERNAL usage cause similar crashes like
this as reported by Tice Rex on the OpenWrt Forum and
reproduced (with symbols) here:
| BUG: Kernel NULL pointer dereference at 0x00000000
| Faulting instruction address: 0xc03ed4b8
| Oops: Kernel access of bad area, sig: 11 [#1]
| BE PAGE_SIZE=4K PowerPC 44x Platform
| CPU: 0 PID: 362 Comm: scsi_eh_1 Not tainted 5.4.163 #0
| NIP:
c03ed4b8 LR:
c03d27e8 CTR:
c03ed36c
| REGS:
cfa59950 TRAP: 0300 Not tainted (5.4.163)
| MSR:
00021000 <CE,ME> CR:
42000222 XER:
00000000
| DEAR:
00000000 ESR:
00000000
| GPR00:
c03d27e8 cfa59a08 cfa55fe0 00000000 0fa46bc0 [...]
| [..]
| NIP [
c03ed4b8] sata_dwc_qc_issue+0x14c/0x254
| LR [
c03d27e8] ata_qc_issue+0x1c8/0x2dc
| Call Trace:
| [
cfa59a08] [
c003f4e0] __cancel_work_timer+0x124/0x194 (unreliable)
| [
cfa59a78] [
c03d27e8] ata_qc_issue+0x1c8/0x2dc
| [
cfa59a98] [
c03d2b3c] ata_exec_internal_sg+0x240/0x524
| [
cfa59b08] [
c03d2e98] ata_exec_internal+0x78/0xe0
| [
cfa59b58] [
c03d30fc] ata_read_log_page.part.38+0x1dc/0x204
| [
cfa59bc8] [
c03d324c] ata_identify_page_supported+0x68/0x130
| [...]
This is because sata_dwc_dma_xfer_complete() NULLs the
dma_pending's next neighbour "chan" (a *dma_chan struct) in
this '32' case right here (line ~735):
> hsdevp->dma_pending[tag] = SATA_DWC_DMA_PENDING_NONE;
Then the next time, a dma gets issued; dma_dwc_xfer_setup() passes
the NULL'd hsdevp->chan to the dmaengine_slave_config() which then
causes the crash.
With this patch, SATA_DWC_QCMD_MAX is now set to ATA_MAX_QUEUE + 1.
This avoids the OOB. But please note, there was a worthwhile discussion
on what ATA_TAG_INTERNAL and ATA_MAX_QUEUE is. And why there should not
be a "fake" 33 command-long queue size.
Ideally, the dw driver should account for the ATA_TAG_INTERNAL.
In Damien Le Moal's words: "... having looked at the driver, it
is a bigger change than just faking a 33rd "tag" that is in fact
not a command tag at all."
Fixes: 28361c403683c ("libata: add extra internal command")
Cc: stable@kernel.org # 4.18+
BugLink: https://github.com/openwrt/openwrt/issues/9505
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>