[PATCH 6/6] scsi: Check sense buffer size at build time

Kees Cook
2018-05-22T18:15:36Z

To avoid introducing problems like those fixed in commit f7068114d45e
("sr: pass down correctly sized SCSI sense buffer"), this creates a macro
wrapper for scsi_execute() that verifies the size of the sense buffer
similar to what was done for command string sizes in commit 3756f6401c30
("exec: avoid gcc-8 warning for get_task_comm").

Another solution could be to add another argument to scsi_execute(),
but this function already takes a lot of arguments and Jens was not fond
of that approach. As there was only a pair of dynamically allocated sense
buffers, this also moves those 96 bytes onto the stack to avoid triggering
the sizeof() check.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/scsi/scsi_lib.c | 6 +++---
include/scsi/scsi_device.h | 12 +++++++++++-
2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e9b4f279d29c..718c2bec4516 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -238,7 +238,7 @@ void scsi_queue_insert(struct scsi_cmnd *cmd, int reason)

/**
- * scsi_execute - insert request and wait for the result
+ * __scsi_execute - insert request and wait for the result
* @sdev: scsi device
* @cmd: scsi command
* @data_direction: data direction
@@ -255,7 +255,7 @@ void scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
* Returns the scsi_cmnd result field if a command was executed, or a negative
* Linux error code if we didn't get that far.
*/
-int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
+int __scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
int data_direction, void *buffer, unsigned bufflen,
unsigned char *sense, struct scsi_sense_hdr *sshdr,
int timeout, int retries, u64 flags, req_flags_t rq_flags,
@@ -309,7 +309,7 @@ int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,

return ret;
}
-EXPORT_SYMBOL(scsi_execute);
+EXPORT_SYMBOL(__scsi_execute);

/*
* Function: scsi_init_cmd_errh()
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 7ae177c8e399..1bb87b6c0ad2 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -426,11 +426,21 @@ extern const char *scsi_device_state_name(enum scsi_device_state);
extern int scsi_is_sdev_device(const struct device *);
extern int scsi_is_target_device(const struct device *);
extern void scsi_sanitize_inquiry_string(unsigned char *s, int len);
-extern int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
+extern int __scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
int data_direction, void *buffer, unsigned bufflen,
unsigned char *sense, struct scsi_sense_hdr *sshdr,
int timeout, int retries, u64 flags,
req_flags_t rq_flags, int *resid);
+/* Make sure any sense buffer is the correct size. */
+#define scsi_execute(sdev, cmd, data_direction, buffer, bufflen, sense, \
+ sshdr, timeout, retries, flags, rq_flags, resid) \
+({ \
+ BUILD_BUG_ON((sense) != NULL && \
+ sizeof(sense) != SCSI_SENSE_BUFFERSIZE); \
+ __scsi_execute(sdev, cmd, data_direction, buffer, bufflen, \
+ sense, sshdr, timeout, retries, flags, rq_flags, \
+ resid); \
+})
static inline int scsi_execute_req(struct scsi_device *sdev,
const unsigned char *cmd, int data_direction, void *buffer,
unsigned bufflen, struct scsi_sense_hdr *sshdr, int timeout,
--
2.17.0