--- /dev/null
+From f23a4d6e07570826fe95023ca1aa96a011fa9f84 Mon Sep 17 00:00:00 2001
+From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
+Date: Wed, 13 Mar 2024 08:21:20 -0300
+Subject: scsi: core: Fix unremoved procfs host directory regression
+
+From: Guilherme G. Piccoli <gpiccoli@igalia.com>
+
+commit f23a4d6e07570826fe95023ca1aa96a011fa9f84 upstream.
+
+Commit fc663711b944 ("scsi: core: Remove the /proc/scsi/${proc_name}
+directory earlier") fixed a bug related to modules loading/unloading, by
+adding a call to scsi_proc_hostdir_rm() on scsi_remove_host(). But that led
+to a potential duplicate call to the hostdir_rm() routine, since it's also
+called from scsi_host_dev_release(). That triggered a regression report,
+which was then fixed by commit be03df3d4bfe ("scsi: core: Fix a procfs host
+directory removal regression"). The fix just dropped the hostdir_rm() call
+from dev_release().
+
+But it happens that this proc directory is created on scsi_host_alloc(),
+and that function "pairs" with scsi_host_dev_release(), while
+scsi_remove_host() pairs with scsi_add_host(). In other words, it seems the
+reason for removing the proc directory on dev_release() was meant to cover
+cases in which a SCSI host structure was allocated, but the call to
+scsi_add_host() didn't happen. And that pattern happens to exist in some
+error paths, for example.
+
+Syzkaller causes that by using USB raw gadget device, error'ing on
+usb-storage driver, at usb_stor_probe2(). By checking that path, we can see
+that the BadDevice label leads to a scsi_host_put() after a SCSI host
+allocation, but there's no call to scsi_add_host() in such path. That leads
+to messages like this in dmesg (and a leak of the SCSI host proc
+structure):
+
+usb-storage 4-1:87.51: USB Mass Storage device detected
+proc_dir_entry 'scsi/usb-storage' already registered
+WARNING: CPU: 1 PID: 3519 at fs/proc/generic.c:377 proc_register+0x347/0x4e0 fs/proc/generic.c:376
+
+The proper fix seems to still call scsi_proc_hostdir_rm() on dev_release(),
+but guard that with the state check for SHOST_CREATED; there is even a
+comment in scsi_host_dev_release() detailing that: such conditional is
+meant for cases where the SCSI host was allocated but there was no calls to
+{add,remove}_host(), like the usb-storage case.
+
+This is what we propose here and with that, the error path of usb-storage
+does not trigger the warning anymore.
+
+Reported-by: syzbot+c645abf505ed21f931b5@syzkaller.appspotmail.com
+Fixes: be03df3d4bfe ("scsi: core: Fix a procfs host directory removal regression")
+Cc: stable@vger.kernel.org
+Cc: Bart Van Assche <bvanassche@acm.org>
+Cc: John Garry <john.g.garry@oracle.com>
+Cc: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
+Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
+Link: https://lore.kernel.org/r/20240313113006.2834799-1-gpiccoli@igalia.com
+Reviewed-by: Bart Van Assche <bvanassche@acm.org>
+Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/scsi/hosts.c | 7 ++++---
+ 1 file changed, 4 insertions(+), 3 deletions(-)
+
+--- a/drivers/scsi/hosts.c
++++ b/drivers/scsi/hosts.c
+@@ -331,12 +331,13 @@ static void scsi_host_dev_release(struct
+
+ if (shost->shost_state == SHOST_CREATED) {
+ /*
+- * Free the shost_dev device name here if scsi_host_alloc()
+- * and scsi_host_put() have been called but neither
++ * Free the shost_dev device name and remove the proc host dir
++ * here if scsi_host_{alloc,put}() have been called but neither
+ * scsi_host_add() nor scsi_host_remove() has been called.
+ * This avoids that the memory allocated for the shost_dev
+- * name is leaked.
++ * name as well as the proc dir structure are leaked.
+ */
++ scsi_proc_hostdir_rm(shost->hostt);
+ kfree(dev_name(&shost->shost_dev));
+ }
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
