[PATCH] [SCSI] gdth: Allocate sense_buffer to prevent NULL pointer dereference

[Sven Schnelle]

Hi,

i'm facing the following kernel oops with the latest git:

--------------------------------------8<--------------------------------------
Stopping MD arrays...failed (no MD subsystem loaded).
Mounting root filesystem read-only...done.
Will now restart.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
IP: [<ffffffff8051a97e>] __gdth_interrupt+0x96e/0xb7f
PGD 7e51e067 PUD 7e6a1067 PMD 0 
Oops: 0002 [1] PREEMPT SMP 
CPU 3 
Modules linked in: nvidia(P) lm85 hwmon_vid hwmon [last unloaded: nvidia]
Pid: 0, comm: swapper Tainted: P         2.6.25-rc4-smp-00134-g84c6f60 #11 
RIP: 0010:[<ffffffff8051a97e>]  [<ffffffff8051a97e>] __gdth_interrupt+0x96e/0xb7f
RSP: 0018:ffff81007fbefed8  EFLAGS: 00010086
RAX: 0000000000000000 RBX: ffff81007e0dda68 RCX: 0000000000000002
RDX: 00000000ffffffff RSI: 0000000000000000 RDI: ffffc20000330000
RBP: ffff81007fbeff08 R08: 0000000000000000 R09: ffff81007f01de70
R10: 0000000000000000 R11: 0000000000000050 R12: ffff810000b10480
R13: ffff810000b104ff R14: ffff81007e214200 R15: 0000000000000009
FS:  0000000000000000(0000) GS:ffff81007f802c80(0000) knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: 0000000000000000 CR3: 000000007e643000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process swapper (pid: 0, threadinfo ffff81007fbe6000, task ffff81007fbe4000)
Stack:  0000000000000046 ffff81007e8a93c0 0000000000000000 0000000000000000
 0000000000000018 0000000000000003 ffff81007fbeff18 ffffffff8051ab9f
 ffff81007fbeff48 ffffffff80258cc2 ffffffff8092e300 ffff81007e8a93c0
Call Trace:
 <IRQ>  [<ffffffff8051ab9f>] gdth_interrupt+0x10/0x12
 [<ffffffff80258cc2>] handle_IRQ_event+0x27/0x57
 [<ffffffff8025a055>] handle_fasteoi_irq+0x9c/0xdc
 [<ffffffff8020def0>] do_IRQ+0x88/0xfc
 [<ffffffff80209ffe>] ? default_idle+0x0/0x5f
 [<ffffffff8020b851>] ret_from_intr+0x0/0xa
 <EOI>  [<ffffffff8020a037>] ? default_idle+0x39/0x5f
 [<ffffffff8020a032>] ? default_idle+0x34/0x5f
 [<ffffffff80209ffe>] ? default_idle+0x0/0x5f
 [<ffffffff8020a11c>] ? cpu_idle+0xbf/0xf5
 [<ffffffff806cd973>] ? start_secondary+0x3e0/0x3ef


Code: 00 04 eb 15 3c 17 75 11 41 0f b6 c5 48 c1 e0 05 41 80 a4 04 92 02 00 00 fb 41 c7 86 18 01 00 00 00 00 00 00 49 8b 86 c0 00 00 00 <c6> 00 00 e9 92 01 00 00 66 89 43 24 41 8b 84 24 68 02 00 00 89 
RIP  [<ffffffff8051a97e>] __gdth_interrupt+0x96e/0xb7f
 RSP <ffff81007fbefed8>
CR2: 0000000000000000
---[ end trace e81e561a458e8791 ]---
Kernel panic - not syncing: Aiee, killing interrupt handler!
Rebooting in 5 seconds..
--------------------------------------8<--------------------------------------

From 2dc63f9f8e61fd1c89f8b4d9b2d174be1c3bfbe2 Mon Sep 17 00:00:00 2001
From: root <root@xxxxxxxxxxxxxxxxxxx>
Date: Sun, 9 Mar 2008 13:25:07 +0100
Subject: 

This fixes a NULL pointer dereference during execution of Internal commands,
where gdth only allocates scp, but not scp->sense_buffer. The rest of
the code assumes that sense_buffer is allocated, which leads to a kernel
oops e.g. on reboot (during cache flush).

So we have two choices here:

a) Allocate the sense_buffer
b) surrounding all accesses to sense_buffer with some if (!internal_command)

I'm using solution a, as this keeps code simpler.

Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxxx>
---
 drivers/scsi/gdth.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/scsi/gdth.c b/drivers/scsi/gdth.c
index 27ebd33..0b2080d 100644
--- a/drivers/scsi/gdth.c
+++ b/drivers/scsi/gdth.c
@@ -493,6 +493,12 @@ int __gdth_execute(struct scsi_device *sdev, gdth_cmd_str *gdtcmd, char *cmnd,
     if (!scp)
         return -ENOMEM;
 
+    scp->sense_buffer = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_KERNEL);
+    if (!scp->sense_buffer) {
+	kfree(scp);
+	return -ENOMEM;
+    }
+
     scp->device = sdev;
     memset(&cmndinfo, 0, sizeof(cmndinfo));
 
@@ -513,6 +519,7 @@ int __gdth_execute(struct scsi_device *sdev, gdth_cmd_str *gdtcmd, char *cmnd,
     rval = cmndinfo.status;
     if (info)
         *info = cmndinfo.info;
+    kfree(scp->sense_buffer);
     kfree(scp);
     return rval;
 }
-- 
1.5.4.3

Cheers,

Sven.

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