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Subject[50/71] libata: fix oops when LPM is used with PMP
2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Tejun Heo <tj@kernel.org>

commit 5f6f12ccf3aa42cfc0c5bde9228df0c843dd63f7 upstream.

ae01b2493c (libata: Implement ATA_FLAG_NO_DIPM and apply it to mcp65)
added ATA_FLAG_NO_DIPM and made ata_eh_set_lpm() check the flag.
However, @ap is NULL if @link points to a PMP link and thus the
unconditional @ap->flags dereference leads to the following oops.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
IP: [<ffffffff813f98e1>] ata_eh_recover+0x9a1/0x1510
...
Pid: 295, comm: scsi_eh_4 Tainted: P 2.6.38.5-core2 #1 System76, Inc. Serval Professional/Serval Professional
RIP: 0010:[<ffffffff813f98e1>] [<ffffffff813f98e1>] ata_eh_recover+0x9a1/0x1510
RSP: 0018:ffff880132defbf0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff880132f40000 RCX: 0000000000000000
RDX: ffff88013377c000 RSI: ffff880132f40000 RDI: 0000000000000000
RBP: ffff880132defce0 R08: ffff88013377dc58 R09: ffff880132defd98
R10: 0000000000000000 R11: 00000000ffffffff R12: 0000000000000000
R13: 0000000000000000 R14: ffff88013377c000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8800bf700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000018 CR3: 0000000001a03000 CR4: 00000000000406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process scsi_eh_4 (pid: 295, threadinfo ffff880132dee000, task ffff880133b416c0)
Stack:
0000000000000000 ffff880132defcc0 0000000000000000 ffff880132f42738
ffffffff813ee8f0 ffffffff813eefe0 ffff880132defd98 ffff88013377f190
ffffffffa00b3e30 ffffffff813ef030 0000000032defc60 ffff880100000000
Call Trace:
[<ffffffff81400867>] sata_pmp_error_handler+0x607/0xc30
[<ffffffffa00b273f>] ahci_error_handler+0x1f/0x70 [libahci]
[<ffffffff813faade>] ata_scsi_error+0x5be/0x900
[<ffffffff813cf724>] scsi_error_handler+0x124/0x650
[<ffffffff810834b6>] kthread+0x96/0xa0
[<ffffffff8100cd64>] kernel_thread_helper+0x4/0x10
Code: 8b 95 70 ff ff ff b8 00 00 00 00 48 3b 9a 10 2e 00 00 48 0f 44 c2 48 89 85 70 ff ff ff 48 8b 8d 70 ff ff ff f6 83 69 02 00 00 01 <48> 8b 41 18 0f 85 48 01 00 00 48 85 c9 74 12 48 8b 51 08 48 83
RIP [<ffffffff813f98e1>] ata_eh_recover+0x9a1/0x1510
RSP <ffff880132defbf0>
CR2: 0000000000000018

Fix it by testing @link->ap->flags instead.

stable: ATA_FLAG_NO_DIPM was added during 2.6.39 cycle but was
backported to 2.6.37 and 38. This is a fix for that and thus
also applicable to 2.6.37 and 38.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: "Nathan A. Mourey II" <nmoureyii@ne.rr.com>
LKML-Reference: <1304555277.2059.2.camel@localhost.localdomain>
Cc: Connor H <cmdkhh@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/ata/libata-eh.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -3276,7 +3276,7 @@ static int ata_eh_set_lpm(struct ata_lin
struct ata_eh_context *ehc = &link->eh_context;
struct ata_device *dev, *link_dev = NULL, *lpm_dev = NULL;
enum ata_lpm_policy old_policy = link->lpm_policy;
- bool no_dipm = ap->flags & ATA_FLAG_NO_DIPM;
+ bool no_dipm = link->ap->flags & ATA_FLAG_NO_DIPM;
unsigned int hints = ATA_LPM_EMPTY | ATA_LPM_HIPM;
unsigned int err_mask;
int rc;



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