FAILED: patch "[PATCH] scsi: ch: Do not keep references to data transfer element" failed to apply to 6.1-stable tree

PATCH New [email protected] 2 participants 2 messages Oct 12 – Oct 13

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[email protected]

author maintainer

2026-10-12 15:21 UTC #0 lore raw

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 27c0f718d3b3c99e6d315308e95d987d0382a8a8
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026101240-identity-dormitory-be3b@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 27c0f718d3b3c99e6d315308e95d987d0382a8a8 Mon Sep 17 00:00:00 2001
From: Ahmed Abdelhaleem Ahmed <[email protected]>
Date: Tue, 22 Sep 2026 15:46:46 +0000
Subject: [PATCH] scsi: ch: Do not keep references to data transfer element
devices

ch_readconfig() looks up the scsi_device of every data transfer element whose SCSI id the changer reports in READ ELEMENT STATUS, and stores it in ch->dt[]. scsi_device_lookup() takes a reference, and nothing ever drops
it: ch_destroy() frees the array with kfree(). ch->dt[] is read nowhere else - it only supplies the vendor, model and revision printed in the same loop.

Once such a drive is removed, its scsi_device can never be released. It stays on the host's device list at its address, so a new device there is refused by anything that walks the list - target_core_pscsi reports "scsi_device_get() failed for H:C:T:L" - and the low-level driver's module can no longer be unloaded. Only a reboot recovers.

It shows with any changer that reports its drives' ids; with the mhvtl virtual library (IBM 3573-TL personality), each create and remove of a library with four drives leaves four references behind, counted by the module's use count in lsmod. With ch not bound the count is unchanged, and with this patch applied it is unchanged too.

Drop the reference as soon as the name has been printed, and remove the now unused dt[] array. That also removes the array leaked when ch_probe() fails after ch_readconfig().

The same leak was reported with an RFC patch in 2022, which was not merged.

Fixes daa6eda65a53 ("[SCSI] add scsi changer driver")

Cc [email protected]

Link https://lore.kernel.org/linux-scsi/[email protected]/ open here

Signed-off-by Ahmed Abdelhaleem Ahmed <[email protected]>

Reviewed-by Laurence Oberman <[email protected]>

Fixes daa6eda65a53 ("[SCSI] add scsi changer driver")

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Martin K. Petersen (Oracle) <[email protected]>

drivers/scsi/ch.c +9 ~~-20~~

index 4010fdbf813c..c36539c83ed1 100644
@@ -112,7 +112,6 @@ typedef struct {
 	int                 minor;
 	char                name[8];
 	struct scsi_device  *device;
-	struct scsi_device  **dt;        /* ptrs to data transfer elements */
 	u_int               firsts[CH_TYPES];
 	u_int               counts[CH_TYPES];
 	u_int		    voltags;

@@ -363,15 +362,10 @@ ch_readconfig(scsi_changer *ch)
 			vendor_labels[i]);
 	}
 
-	/* look up the devices of the data transfer elements */
-	ch->dt = kzalloc_objs(*ch->dt, ch->counts[CHET_DT]);
-
-	if (!ch->dt) {
-		kfree(buffer);
-		return -ENOMEM;
-	}
-
+	/* report the devices of the data transfer elements */
 	for (elem = 0; elem < ch->counts[CHET_DT]; elem++) {
+		struct scsi_device *sdev;
+
 		id  = -1;
 		lun = 0;
 		if (elem < CH_DT_MAX  &&  -1 != dt_id[elem]) {

@@ -387,10 +381,8 @@ ch_readconfig(scsi_changer *ch)
 			VPRINTK(KERN_INFO, "dt 0x%x: ",elem+ch->firsts[CHET_DT]);
 			if (data[6] & 0x80) {
 				VPRINTK(KERN_CONT, "not this SCSI bus\n");
-				ch->dt[elem] = NULL;
 			} else if (0 == (data[6] & 0x30)) {
 				VPRINTK(KERN_CONT, "ID/LUN unknown\n");
-				ch->dt[elem] = NULL;
 			} else {
 				id  = ch->device->id;
 				lun = 0;

@@ -400,18 +392,16 @@ ch_readconfig(scsi_changer *ch)
 		}
 		if (-1 != id) {
 			VPRINTK(KERN_CONT, "ID %i, LUN %i, ",id,lun);
-			ch->dt[elem] =
-				scsi_device_lookup(ch->device->host,
-						   ch->device->channel,
-						   id,lun);
-			if (!ch->dt[elem]) {
+			sdev = scsi_device_lookup(ch->device->host,
+						  ch->device->channel,
+						  id, lun);
+			if (!sdev) {
 				/* should not happen */
 				VPRINTK(KERN_CONT, "Huh? device not found!\n");
 			} else {
 				VPRINTK(KERN_CONT, "name: %8.8s %16.16s %4.4s\n",
-					ch->dt[elem]->vendor,
-					ch->dt[elem]->model,
-					ch->dt[elem]->rev);
+					sdev->vendor, sdev->model, sdev->rev);
+				scsi_device_put(sdev);
 			}
 		}
 	}

@@ -575,7 +565,6 @@ static void ch_destroy(struct kref *ref)
 	scsi_changer *ch = container_of(ref, scsi_changer, ref);
 
 	ch->device = NULL;
-	kfree(ch->dt);
 	kfree(ch);
 }

Sasha Levin

maintainer

2026-10-13 16:53 UTC #1 lore raw

PATCH 1/1 scsi: ch: Do not keep references to data transfer element devices

From: Ahmed Abdelhaleem Ahmed <[email protected]>

[ Upstream commit 27c0f718d3b3c99e6d315308e95d987d0382a8a8 ]

Drop the reference as soon as the name has been printed, and remove the now unused dt[] array. That also removes the array leaked when ch_probe() fails after ch_readconfig().

The same leak was reported with an RFC patch in 2022, which was not merged.

Fixes daa6eda65a53 ("[SCSI] add scsi changer driver")

Cc [email protected]

Link https://lore.kernel.org/linux-scsi/[email protected]/ open here

Signed-off-by Ahmed Abdelhaleem Ahmed <[email protected]>

Reviewed-by Laurence Oberman <[email protected]>

Fixes daa6eda65a53 ("[SCSI] add scsi changer driver")

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Martin K. Petersen (Oracle) <[email protected]>

[ sashal: Adjusted allocation removal for kcalloc() instead of kzalloc_objs(). ]

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/scsi/ch.c | 30 +++++++++---------------------
 1 file changed, 9 insertions(+), 21 deletions(-)

drivers/scsi/ch.c +9 ~~-21~~

index 7ab29eaec6f38..fa0317402ba4e 100644
@@ -110,7 +110,6 @@ typedef struct {
 	int                 minor;
 	char                name[8];
 	struct scsi_device  *device;
-	struct scsi_device  **dt;        /* ptrs to data transfer elements */
 	u_int               firsts[CH_TYPES];
 	u_int               counts[CH_TYPES];
 	u_int               unit_attention;

@@ -357,16 +356,10 @@ ch_readconfig(scsi_changer *ch)
 			vendor_labels[i]);
 	}
 
-	/* look up the devices of the data transfer elements */
-	ch->dt = kcalloc(ch->counts[CHET_DT], sizeof(*ch->dt),
-			 GFP_KERNEL);
-
-	if (!ch->dt) {
-		kfree(buffer);
-		return -ENOMEM;
-	}
-
+	/* report the devices of the data transfer elements */
 	for (elem = 0; elem < ch->counts[CHET_DT]; elem++) {
+		struct scsi_device *sdev;
+
 		id  = -1;
 		lun = 0;
 		if (elem < CH_DT_MAX  &&  -1 != dt_id[elem]) {

@@ -382,10 +375,8 @@ ch_readconfig(scsi_changer *ch)
 			VPRINTK(KERN_INFO, "dt 0x%x: ",elem+ch->firsts[CHET_DT]);
 			if (data[6] & 0x80) {
 				VPRINTK(KERN_CONT, "not this SCSI bus\n");
-				ch->dt[elem] = NULL;
 			} else if (0 == (data[6] & 0x30)) {
 				VPRINTK(KERN_CONT, "ID/LUN unknown\n");
-				ch->dt[elem] = NULL;
 			} else {
 				id  = ch->device->id;
 				lun = 0;

@@ -395,18 +386,16 @@ ch_readconfig(scsi_changer *ch)
 		}
 		if (-1 != id) {
 			VPRINTK(KERN_CONT, "ID %i, LUN %i, ",id,lun);
-			ch->dt[elem] =
-				scsi_device_lookup(ch->device->host,
-						   ch->device->channel,
-						   id,lun);
-			if (!ch->dt[elem]) {
+			sdev = scsi_device_lookup(ch->device->host,
+						  ch->device->channel,
+						  id, lun);
+			if (!sdev) {
 				/* should not happen */
 				VPRINTK(KERN_CONT, "Huh? device not found!\n");
 			} else {
 				VPRINTK(KERN_CONT, "name: %8.8s %16.16s %4.4s\n",
-					ch->dt[elem]->vendor,
-					ch->dt[elem]->model,
-					ch->dt[elem]->rev);
+					sdev->vendor, sdev->model, sdev->rev);
+				scsi_device_put(sdev);
 			}
 		}
 	}

@@ -570,7 +559,6 @@ static void ch_destroy(struct kref *ref)
 	scsi_changer *ch = container_of(ref, scsi_changer, ref);
 
 	ch->device = NULL;
-	kfree(ch->dt);
 	kfree(ch);
 }

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