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compat: scsi: sg: fix v3 compat read/write interface
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In the v5.4 merge window, a cleanup patch from Al Viro conflicted
with my rework of the compat handling for sg.c read(). Linus Torvalds
did a correct merge but pointed out that the resulting code is still
unsatisfactory.

I later noticed that the sg_new_read() function still gets the compat
mode wrong, when the 'count' argument is large enough to pass a
compat_sg_io_hdr object, but not a nativ sg_io_hdr.

To address both of these, move the definition of compat_sg_io_hdr
into a scsi/sg.h to make it visible to sg.c and rewrite the logic
for reading req_pack_id as well as the size check to a simpler
version that gets the expected results.

Fixes: c35a5cf ("scsi: sg: sg_read(): simplify reading ->pack_id of userland sg_io_hdr_t")
Fixes: 98aaaec ("compat_ioctl: reimplement SG_IO handling")
Reviewed-by: Ben Hutchings <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
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@arndb
arndb committed Jan 3, 2020
1 parent 202bf8d commit 78ed001
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Showing 3 changed files with 90 additions and 95 deletions.
29 changes: 1 addition & 28 deletions block/scsi_ioctl.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#include <scsi/scsi.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/sg.h>

struct blk_cmd_filter {
unsigned long read_ok[BLK_SCSI_CMD_PER_LONG];
Expand Down Expand Up @@ -550,34 +551,6 @@ static inline int blk_send_start_stop(struct request_queue *q,
return __blk_send_generic(q, bd_disk, GPCMD_START_STOP_UNIT, data);
}

#ifdef CONFIG_COMPAT
struct compat_sg_io_hdr {
compat_int_t interface_id; /* [i] 'S' for SCSI generic (required) */
compat_int_t dxfer_direction; /* [i] data transfer direction */
unsigned char cmd_len; /* [i] SCSI command length ( <= 16 bytes) */
unsigned char mx_sb_len; /* [i] max length to write to sbp */
unsigned short iovec_count; /* [i] 0 implies no scatter gather */
compat_uint_t dxfer_len; /* [i] byte count of data transfer */
compat_uint_t dxferp; /* [i], [*io] points to data transfer memory
or scatter gather list */
compat_uptr_t cmdp; /* [i], [*i] points to command to perform */
compat_uptr_t sbp; /* [i], [*o] points to sense_buffer memory */
compat_uint_t timeout; /* [i] MAX_UINT->no timeout (unit: millisec) */
compat_uint_t flags; /* [i] 0 -> default, see SG_FLAG... */
compat_int_t pack_id; /* [i->o] unused internally (normally) */
compat_uptr_t usr_ptr; /* [i->o] unused internally */
unsigned char status; /* [o] scsi status */
unsigned char masked_status; /* [o] shifted, masked scsi status */
unsigned char msg_status; /* [o] messaging level data (optional) */
unsigned char sb_len_wr; /* [o] byte count actually written to sbp */
unsigned short host_status; /* [o] errors from host adapter */
unsigned short driver_status; /* [o] errors from software driver */
compat_int_t resid; /* [o] dxfer_len - actual_transferred */
compat_uint_t duration; /* [o] time taken by cmd (unit: millisec) */
compat_uint_t info; /* [o] auxiliary information */
};
#endif

int put_sg_io_hdr(const struct sg_io_hdr *hdr, void __user *argp)
{
#ifdef CONFIG_COMPAT
Expand Down
126 changes: 59 additions & 67 deletions drivers/scsi/sg.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -405,6 +405,38 @@ sg_release(struct inode *inode, struct file *filp)
return 0;
}

static int get_sg_io_pack_id(int *pack_id, void __user *buf, size_t count)
{
struct sg_header __user *old_hdr = buf;
int reply_len;

if (count >= SZ_SG_HEADER) {
/* negative reply_len means v3 format, otherwise v1/v2 */
if (get_user(reply_len, &old_hdr->reply_len))
return -EFAULT;

if (reply_len >= 0)
return get_user(*pack_id, &old_hdr->pack_id);

if (in_compat_syscall() &&
count >= sizeof(struct compat_sg_io_hdr)) {
struct compat_sg_io_hdr __user *hp = buf;

return get_user(*pack_id, &hp->pack_id);
}

if (count >= sizeof(struct sg_io_hdr)) {
struct sg_io_hdr __user *hp = buf;

return get_user(*pack_id, &hp->pack_id);
}
}

/* no valid header was passed, so ignore the pack_id */
*pack_id = -1;
return 0;
}

static ssize_t
sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
{
Expand All @@ -413,8 +445,8 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
Sg_request *srp;
int req_pack_id = -1;
sg_io_hdr_t *hp;
struct sg_header *old_hdr = NULL;
int retval = 0;
struct sg_header *old_hdr;
int retval;

/*
* This could cause a response to be stranded. Close the associated
Expand All @@ -429,79 +461,34 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
"sg_read: count=%d\n", (int) count));

if (sfp->force_packid && (count >= SZ_SG_HEADER)) {
old_hdr = memdup_user(buf, SZ_SG_HEADER);
if (IS_ERR(old_hdr))
return PTR_ERR(old_hdr);
if (old_hdr->reply_len < 0) {
if (count >= SZ_SG_IO_HDR) {
/*
* This is stupid.
*
* We're copying the whole sg_io_hdr_t from user
* space just to get the 'pack_id' field. But the
* field is at different offsets for the compat
* case, so we'll use "get_sg_io_hdr()" to copy
* the whole thing and convert it.
*
* We could do something like just calculating the
* offset based of 'in_compat_syscall()', but the
* 'compat_sg_io_hdr' definition is in the wrong
* place for that.
*/
sg_io_hdr_t *new_hdr;
new_hdr = kmalloc(SZ_SG_IO_HDR, GFP_KERNEL);
if (!new_hdr) {
retval = -ENOMEM;
goto free_old_hdr;
}
retval = get_sg_io_hdr(new_hdr, buf);
req_pack_id = new_hdr->pack_id;
kfree(new_hdr);
if (retval) {
retval = -EFAULT;
goto free_old_hdr;
}
}
} else
req_pack_id = old_hdr->pack_id;
}
if (sfp->force_packid)
retval = get_sg_io_pack_id(&req_pack_id, buf, count);
if (retval)
return retval;

srp = sg_get_rq_mark(sfp, req_pack_id);
if (!srp) { /* now wait on packet to arrive */
if (atomic_read(&sdp->detaching)) {
retval = -ENODEV;
goto free_old_hdr;
}
if (filp->f_flags & O_NONBLOCK) {
retval = -EAGAIN;
goto free_old_hdr;
}
if (atomic_read(&sdp->detaching))
return -ENODEV;
if (filp->f_flags & O_NONBLOCK)
return -EAGAIN;
retval = wait_event_interruptible(sfp->read_wait,
(atomic_read(&sdp->detaching) ||
(srp = sg_get_rq_mark(sfp, req_pack_id))));
if (atomic_read(&sdp->detaching)) {
retval = -ENODEV;
goto free_old_hdr;
}
if (retval) {
if (atomic_read(&sdp->detaching))
return -ENODEV;
if (retval)
/* -ERESTARTSYS as signal hit process */
goto free_old_hdr;
}
}
if (srp->header.interface_id != '\0') {
retval = sg_new_read(sfp, buf, count, srp);
goto free_old_hdr;
return retval;
}
if (srp->header.interface_id != '\0')
return sg_new_read(sfp, buf, count, srp);

hp = &srp->header;
if (old_hdr == NULL) {
old_hdr = kmalloc(SZ_SG_HEADER, GFP_KERNEL);
if (! old_hdr) {
retval = -ENOMEM;
goto free_old_hdr;
}
}
memset(old_hdr, 0, SZ_SG_HEADER);
old_hdr = kzalloc(SZ_SG_HEADER, GFP_KERNEL);
if (!old_hdr)
return -ENOMEM;

old_hdr->reply_len = (int) hp->timeout;
old_hdr->pack_len = old_hdr->reply_len; /* old, strange behaviour */
old_hdr->pack_id = hp->pack_id;
Expand Down Expand Up @@ -575,7 +562,12 @@ sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
int err = 0, err2;
int len;

if (count < SZ_SG_IO_HDR) {
if (in_compat_syscall()) {
if (count < sizeof(struct compat_sg_io_hdr)) {
err = -EINVAL;
goto err_out;
}
} else if (count < SZ_SG_IO_HDR) {
err = -EINVAL;
goto err_out;
}
Expand Down
30 changes: 30 additions & 0 deletions include/scsi/sg.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,36 @@ typedef struct sg_io_hdr
unsigned int info; /* [o] auxiliary information */
} sg_io_hdr_t; /* 64 bytes long (on i386) */

#if defined(__KERNEL__)
#include <linux/compat.h>

struct compat_sg_io_hdr {
compat_int_t interface_id; /* [i] 'S' for SCSI generic (required) */
compat_int_t dxfer_direction; /* [i] data transfer direction */
unsigned char cmd_len; /* [i] SCSI command length ( <= 16 bytes) */
unsigned char mx_sb_len; /* [i] max length to write to sbp */
unsigned short iovec_count; /* [i] 0 implies no scatter gather */
compat_uint_t dxfer_len; /* [i] byte count of data transfer */
compat_uint_t dxferp; /* [i], [*io] points to data transfer memory
or scatter gather list */
compat_uptr_t cmdp; /* [i], [*i] points to command to perform */
compat_uptr_t sbp; /* [i], [*o] points to sense_buffer memory */
compat_uint_t timeout; /* [i] MAX_UINT->no timeout (unit: millisec) */
compat_uint_t flags; /* [i] 0 -> default, see SG_FLAG... */
compat_int_t pack_id; /* [i->o] unused internally (normally) */
compat_uptr_t usr_ptr; /* [i->o] unused internally */
unsigned char status; /* [o] scsi status */
unsigned char masked_status; /* [o] shifted, masked scsi status */
unsigned char msg_status; /* [o] messaging level data (optional) */
unsigned char sb_len_wr; /* [o] byte count actually written to sbp */
unsigned short host_status; /* [o] errors from host adapter */
unsigned short driver_status; /* [o] errors from software driver */
compat_int_t resid; /* [o] dxfer_len - actual_transferred */
compat_uint_t duration; /* [o] time taken by cmd (unit: millisec) */
compat_uint_t info; /* [o] auxiliary information */
};
#endif

#define SG_INTERFACE_ID_ORIG 'S'

/* Use negative values to flag difference from original sg_header structure */
Expand Down

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