linux-kernel - [PATCH 3.16 25/61] scsi: sg: Change next_cmd

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Message-ID: <lsq.1591725832.42461519@decadent.org.uk>
Date:   Tue, 09 Jun 2020 19:04:16 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>
Subject: [PATCH 3.16 25/61] scsi: sg: Change next_cmd_len handling to
 mirror upstream

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@...adent.org.uk>

Change the type of next_cmd_len to unsigned char, done in upstream
commit 65c26a0f3969 "sg: relax 16 byte cdb restriction".

Move the range check from sg_write() to sg_ioctl(), which was done by
that commit and commit bf33f87dd04c "scsi: sg: check length passed to
SG_NEXT_CMD_LEN".  Continue limiting the command length to
MAX_COMMAND_SIZE (16).

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -160,7 +160,7 @@ typedef struct sg_fd {		/* holds the sta
 	char low_dma;		/* as in parent but possibly overridden to 1 */
 	char force_packid;	/* 1 -> pack_id input to read(), 0 -> ignored */
 	char cmd_q;		/* 1 -> allow command queuing, 0 -> don't */
-	char next_cmd_len;	/* 0 -> automatic (def), >0 -> use on next write() */
+	unsigned char next_cmd_len; /* 0: automatic, >0: use on next write() */
 	char keep_orphan;	/* 0 -> drop orphan (def), 1 -> keep for read() */
 	char mmap_called;	/* 0 -> mmap() never called on this fd */
 	struct kref f_ref;
@@ -653,12 +653,6 @@ sg_write(struct file *filp, const char _
 	buf += SZ_SG_HEADER;
 	__get_user(opcode, buf);
 	if (sfp->next_cmd_len > 0) {
-		if (sfp->next_cmd_len > MAX_COMMAND_SIZE) {
-			SCSI_LOG_TIMEOUT(1, printk("sg_write: command length too long\n"));
-			sfp->next_cmd_len = 0;
-			sg_remove_request(sfp, srp);
-			return -EIO;
-		}
 		cmd_size = sfp->next_cmd_len;
 		sfp->next_cmd_len = 0;	/* reset so only this write() effected */
 	} else {
@@ -1045,6 +1039,8 @@ sg_ioctl(struct file *filp, unsigned int
 		result = get_user(val, ip);
 		if (result)
 			return result;
+		if (val > MAX_COMMAND_SIZE)
+			return -ENOMEM;
 		sfp->next_cmd_len = (val > 0) ? val : 0;
 		return 0;
 	case SG_GET_VERSION_NUM: