This is a note to let you know that I've just added the patch titled

scsi: mac_esp: Replace bogus memory barrier with spinlock

to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: scsi-mac_esp-replace-bogus-memory-barrier-with-spinlock.patch and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Mar 22 15:16:04 CET 2018

From: Finn Thain fthain@telegraphics.com.au Date: Sun, 2 Apr 2017 17:08:05 +1000 Subject: scsi: mac_esp: Replace bogus memory barrier with spinlock

From: Finn Thain fthain@telegraphics.com.au

[ Upstream commit 4da2b1eb230ba4ad19b58984dc52e05b1073df5f ]

Commit da244654c66e ("[SCSI] mac_esp: fix for quadras with two esp chips") added mac_scsi_esp_intr() to handle the IRQ lines from a pair of on-board ESP chips (a normal shared IRQ did not work).

Proper mutual exclusion was missing from that patch. This patch fixes race conditions between comparison and assignment of esp_chips[] pointers.

Signed-off-by: Finn Thain fthain@telegraphics.com.au Reviewed-by: Michael Schmitz schmitzmic@gmail.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/scsi/mac_esp.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-)

--- a/drivers/scsi/mac_esp.c +++ b/drivers/scsi/mac_esp.c @@ -55,6 +55,7 @@ struct mac_esp_priv { int error; }; static struct esp *esp_chips[2]; +static DEFINE_SPINLOCK(esp_chips_lock);

#define MAC_ESP_GET_PRIV(esp) ((struct mac_esp_priv *) \ platform_get_drvdata((struct platform_device *) \ @@ -562,15 +563,18 @@ static int esp_mac_probe(struct platform }

host->irq = IRQ_MAC_SCSI; - esp_chips[dev->id] = esp; - mb(); - if (esp_chips[!dev->id] == NULL) { - err = request_irq(host->irq, mac_scsi_esp_intr, 0, "ESP", NULL); - if (err < 0) { - esp_chips[dev->id] = NULL; - goto fail_free_priv; - } + + /* The request_irq() call is intended to succeed for the first device + * and fail for the second device. + */ + err = request_irq(host->irq, mac_scsi_esp_intr, 0, "ESP", NULL); + spin_lock(&esp_chips_lock); + if (err < 0 && esp_chips[!dev->id] == NULL) { + spin_unlock(&esp_chips_lock); + goto fail_free_priv; } + esp_chips[dev->id] = esp; + spin_unlock(&esp_chips_lock);

err = scsi_esp_register(esp, &dev->dev); if (err) @@ -579,8 +583,13 @@ static int esp_mac_probe(struct platform return 0;

fail_free_irq: - if (esp_chips[!dev->id] == NULL) + spin_lock(&esp_chips_lock); + esp_chips[dev->id] = NULL; + if (esp_chips[!dev->id] == NULL) { + spin_unlock(&esp_chips_lock); free_irq(host->irq, esp); + } else + spin_unlock(&esp_chips_lock); fail_free_priv: kfree(mep); fail_free_command_block: @@ -599,9 +608,13 @@ static int esp_mac_remove(struct platfor

scsi_esp_unregister(esp);

+ spin_lock(&esp_chips_lock); esp_chips[dev->id] = NULL; - if (!(esp_chips[0] || esp_chips[1])) + if (esp_chips[!dev->id] == NULL) { + spin_unlock(&esp_chips_lock); free_irq(irq, NULL); + } else + spin_unlock(&esp_chips_lock);

kfree(mep);

Patches currently in stable-queue which might be from fthain@telegraphics.com.au are

queue-3.18/scsi-mac_esp-replace-bogus-memory-barrier-with-spinlock.patch