[PATCH 5.4 168/367] scsi: qedf: Do not touch __user pointer in qedf_dbg_debug_cmd_read() directly

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5.4-stable review patch.  If anyone has any objections, please let me know.


From: Oleksandr Natalenko <oleksandr@xxxxxxxxxx>

[ Upstream commit 31b5991a9a91ba97237ac9da509d78eec453ff72 ]

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@xxxxxxxxxx/
Link: https://lore.kernel.org/linux-scsi/20230726101236.11922-1-skashyap@xxxxxxxxxxx/
Cc: Saurav Kashyap <skashyap@xxxxxxxxxxx>
Cc: Rob Evers <revers@xxxxxxxxxx>
Cc: Johannes Thumshirn <Johannes.Thumshirn@xxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Jozef Bacik <jobacik@xxxxxxxxxx>
Cc: Laurence Oberman <loberman@xxxxxxxxxx>
Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxx>
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
Cc: GR-QLogic-Storage-Upstream@xxxxxxxxxxx
Cc: linux-scsi@xxxxxxxxxxxxxxx
Reviewed-by: Laurence Oberman <loberman@xxxxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Tested-by: Laurence Oberman <loberman@xxxxxxxxxx>
Acked-by: Saurav Kashyap <skashyap@xxxxxxxxxxx>
Signed-off-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230731084034.37021-3-oleksandr@xxxxxxxxxx
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
 drivers/scsi/qedf/qedf_debugfs.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/qedf/qedf_debugfs.c b/drivers/scsi/qedf/qedf_debugfs.c
index 88378a277a015..5e638732d6852 100644
--- a/drivers/scsi/qedf/qedf_debugfs.c
+++ b/drivers/scsi/qedf/qedf_debugfs.c
@@ -140,15 +140,14 @@ 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

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