scsi: qedf: Do not touch __user pointer in qedf_dbg_debug_cmd_read() directly

The qedf_dbg_debug_cmd_read() function invokes sprintf() directly on a
__user pointer, which may crash the kernel.

Avoid doing that by using a small on-stack buffer for scnprintf() and then
calling simple_read_from_buffer() which does a proper copy_to_user() call.

Fixes: 61d8658b4a43 ("scsi: qedf: Add QLogic FastLinQ offload FCoE driver framework.")
Link: https://lore.kernel.org/lkml/20230724120241.40495-1-oleksandr@redhat.com/
Link: https://lore.kernel.org/linux-scsi/20230726101236.11922-1-skashyap@marvell.com/
Cc: Saurav Kashyap <skashyap@marvell.com>
Cc: Rob Evers <revers@redhat.com>
Cc: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Jozef Bacik <jobacik@redhat.com>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: GR-QLogic-Storage-Upstream@marvell.com
Cc: linux-scsi@vger.kernel.org
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Laurence Oberman <loberman@redhat.com>
Acked-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Oleksandr Natalenko <oleksandr@redhat.com>
Link: https://lore.kernel.org/r/20230731084034.37021-3-oleksandr@redhat.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/qedf/qedf_debugfs.c b/drivers/scsi/qedf/qedf_debugfs.c
index 3eb4334ac6a3212ac12bd908f8cea0b1737c3db6..1c5716540e465b16f417fe60773c5c151bb94b07 100644 (file)
--- a/drivers/scsi/qedf/qedf_debugfs.c
+++ b/drivers/scsi/qedf/qedf_debugfs.c
@@ -138,15 +138,14 @@ qedf_dbg_debug_cmd_read(struct file *filp, char __user *buffer, size_t count,
                        loff_t *ppos)
 {
        int cnt;
+       char cbuf[32];
        struct qedf_dbg_ctx *qedf_dbg =
                                (struct qedf_dbg_ctx *)filp->private_data;
 
        QEDF_INFO(qedf_dbg, QEDF_LOG_DEBUGFS, "debug mask=0x%x\n", qedf_debug);
-       cnt = sprintf(buffer, "debug mask = 0x%x\n", qedf_debug);
+       cnt = scnprintf(cbuf, sizeof(cbuf), "debug mask = 0x%x\n", qedf_debug);
 
-       cnt = min_t(int, count, cnt - *ppos);
-       *ppos += cnt;
-       return cnt;
+       return simple_read_from_buffer(buffer, count, ppos, cbuf, cnt);
 }
 
 static ssize_t