ide: fix regression caused by ide_device_{get,put}() addition (take 2)

On Monday 28 July 2008, Benjamin Herrenschmidt wrote:

[...]

> Vector: 300 (Data Access) at [c58b7b80]
>     pc: c014f264: elv_may_queue+0x10/0x44
>     lr: c0152750: get_request+0x2c/0x2c0
>     sp: c58b7c30
>    msr: 1032
>    dar: c
>  dsisr: 40000000
>   current = 0xc58aaae0
>     pid   = 854, comm = media-bay
> enter ? for help
> mon> t
> [c58b7c40] c0152750 get_request+0x2c/0x2c0
> [c58b7c70] c0152a08 get_request_wait+0x24/0xec
> [c58b7cc0] c0225674 ide_cd_queue_pc+0x58/0x1a0
> [c58b7d40] c022672c ide_cdrom_packet+0x9c/0xdc
> [c58b7d70] c0261810 cdrom_get_disc_info+0x60/0xd0
> [c58b7dc0] c026208c cdrom_mrw_exit+0x1c/0x11c
> [c58b7e30] c0260f7c unregister_cdrom+0x84/0xe8
> [c58b7e50] c022395c ide_cd_release+0x80/0x84
> [c58b7e70] c0163650 kref_put+0x54/0x6c
> [c58b7e80] c0223884 ide_cd_put+0x40/0x5c
> [c58b7ea0] c0211100 generic_ide_remove+0x28/0x3c
> [c58b7eb0] c01e9d34 __device_release_driver+0x78/0xb4
> [c58b7ec0] c01e9e44 device_release_driver+0x28/0x44
> [c58b7ee0] c01e8f7c bus_remove_device+0xac/0xd8
> [c58b7f00] c01e7424 device_del+0x104/0x198
> [c58b7f20] c01e74d0 device_unregister+0x18/0x30
> [c58b7f40] c02121c4 __ide_port_unregister_devices+0x6c/0x88
> [c58b7f60] c0212398 ide_port_unregister_devices+0x38/0x80
> [c58b7f80] c0208ca4 media_bay_step+0x1cc/0x5c0
> [c58b7fb0] c0209124 media_bay_task+0x8c/0xcc
> [c58b7fd0] c00485c0 kthread+0x48/0x84
> [c58b7ff0] c0011b20 kernel_thread+0x44/0x60

The guilty commit turned out to be 08da591e14cf87247ec09b17c350235157a92fc3
("ide: add ide_device_{get,put}() helpers").  ide_device_put() is called
before kref_put() in ide_cd_put() so IDE device is already gone by the time
ide_cd_release() is reached.

Fix it by calling ide_device_get() before kref_get() and ide_device_put()
after kref_put() in all affected device drivers.

v2:
Brown paper bag time.  In v1 cd->drive was referenced after dropping last
reference on cd object (which could result in OOPS in ide_device_put() as
reported/debugged by Mariusz Kozlowski).  Fix it by caching cd->drive in
the local variable (fix other device drivers too).

Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reported-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Borislav Petkov <petkovbb@gmail.com>
Tested-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Tested-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index e617cf08aef6..e19caa1453a3 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -66,11 +66,11 @@ static struct cdrom_info *ide_cd_get(struct gendisk *disk)
         mutex_lock(&idecd_ref_mutex);
         cd = ide_cd_g(disk);
         if (cd) {
-                kref_get(&cd->kref);
-                if (ide_device_get(cd->drive)) {
-                        kref_put(&cd->kref, ide_cd_release);
+                if (ide_device_get(cd->drive))
                         cd = NULL;
-                }
+                else
+                        kref_get(&cd->kref);
+
         }
         mutex_unlock(&idecd_ref_mutex);
         return cd;
@@ -78,9 +78,11 @@ static struct cdrom_info *ide_cd_get(struct gendisk *disk)
 
 static void ide_cd_put(struct cdrom_info *cd)
 {
+        ide_drive_t *drive = cd->drive;
+
         mutex_lock(&idecd_ref_mutex);
-        ide_device_put(cd->drive);
         kref_put(&cd->kref, ide_cd_release);
+        ide_device_put(drive);
         mutex_unlock(&idecd_ref_mutex);
 }