[PATCH v15 39/45] sg: add mmap_sz tracking

Douglas Gilbert
2021-01-26T05:30:43Z

Track mmap_sz from prior mmap(2) call, per sg file descriptor. Also
reset this value whenever munmap(2) is called. Fail SG_FLAG_MMAP_IO
uses if mmap(2) hasn't been called or the memory associated with it
is not large enough for the current request.

Remove SG_FFD_MMAP_CALLED bit as it can be deduced from
sfp->mmap_sz where a value of 0 implies no mmap() call active.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
---
drivers/scsi/sg.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index c7c59cd6af23..9512ebc064cc 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -122,8 +122,7 @@ enum sg_rq_state { /* N.B. sg_rq_state_arr assumes SG_RS_AWAIT_RCV==2 */
#define SG_FFD_FORCE_PACKID 0 /* receive only given pack_id/tag */
#define SG_FFD_CMD_Q 1 /* clear: only 1 active req per fd */
#define SG_FFD_KEEP_ORPHAN 2 /* policy for this fd */
-#define SG_FFD_MMAP_CALLED 3 /* mmap(2) system call made on fd */
-#define SG_FFD_Q_AT_TAIL 5 /* set: queue reqs at tail of blk q */
+#define SG_FFD_Q_AT_TAIL 3 /* set: queue reqs at tail of blk q */

/* Bit positions (flags) for sg_device::fdev_bm bitmask follow */
#define SG_FDEV_EXCLUDE 0 /* have fd open with O_EXCL */
@@ -232,6 +231,7 @@ struct sg_fd { /* holds the state of a file descriptor */
atomic_t waiting; /* number of requests awaiting receive */
atomic_t req_cnt; /* number of requests */
int sgat_elem_sz; /* initialized to scatter_elem_sz */
+ int mmap_sz; /* byte size of previous mmap() call */
unsigned long ffd_bm[1]; /* see SG_FFD_* defines above */
pid_t tid; /* thread id when opened */
u8 next_cmd_len; /* 0: automatic, >0: use on next write() */
@@ -725,10 +725,14 @@ sg_write(struct file *filp, const char __user *p, size_t count, loff_t *ppos)
static inline int
sg_chk_mmap(struct sg_fd *sfp, int rq_flags, int len)
{
+ if (unlikely(sfp->mmap_sz == 0))
+ return -EBADFD;
if (atomic_read(&sfp->submitted) > 0)
return -EBUSY; /* already active requests on fd */
if (len > sfp->rsv_srp->sgat_h.buflen)
return -ENOMEM; /* MMAP_IO size must fit in reserve */
+ if (unlikely(len > sfp->mmap_sz))
+ return -ENOMEM; /* MMAP_IO size can't exceed mmap() size */
if (rq_flags & SG_FLAG_DIRECT_IO)
return -EINVAL; /* not both MMAP_IO and DIRECT_IO */
return 0;
@@ -1800,8 +1804,7 @@ sg_set_reserved_sz(struct sg_fd *sfp, int want_rsv_sz)
res = -EPROTO;
goto fini;
}
- if (SG_RS_ACTIVE(o_srp) ||
- test_bit(SG_FFD_MMAP_CALLED, sfp->ffd_bm)) {
+ if (SG_RS_ACTIVE(o_srp) || sfp->mmap_sz > 0) {
res = -EBUSY;
goto fini;
}
@@ -2262,6 +2265,7 @@ sg_vma_close(struct vm_area_struct *vma)
pr_warn("%s: sfp null\n", __func__);
return;
}
+ sfp->mmap_sz = 0;
kref_put(&sfp->f_ref, sg_remove_sfp); /* get in: sg_vma_open() */
}

@@ -2352,7 +2356,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
req_sz = vma->vm_end - vma->vm_start;
SG_LOG(3, sfp, "%s: vm_start=%pK, len=%d\n", __func__,
(void *)vma->vm_start, (int)req_sz);
- if (vma->vm_pgoff) {
+ if (unlikely(vma->vm_pgoff || req_sz < SG_DEF_SECTOR_SZ)) {
res = -EINVAL; /* only an offset of 0 accepted */
goto fini;
}
@@ -2366,7 +2370,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
res = -ENOMEM;
goto fini;
}
- if (test_and_set_bit(SG_FFD_MMAP_CALLED, sfp->ffd_bm)) {
+ if (sfp->mmap_sz > 0) {
SG_LOG(1, sfp, "%s: multiple invocations on this fd\n",
__func__);
res = -EADDRINUSE;
@@ -2383,6 +2387,7 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
goto fini;
}
}
+ sfp->mmap_sz = req_sz;
vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_private_data = sfp;
vma->vm_ops = &sg_mmap_vm_ops;
@@ -4048,8 +4053,7 @@ sg_proc_debug_fd(struct sg_fd *fp, char *obp, int len, unsigned long idx)
(int)test_bit(SG_FFD_FORCE_PACKID, fp->ffd_bm),
(int)test_bit(SG_FFD_KEEP_ORPHAN, fp->ffd_bm),
fp->ffd_bm[0]);
- n += scnprintf(obp + n, len - n, " mmap_called=%d\n",
- test_bit(SG_FFD_MMAP_CALLED, fp->ffd_bm));
+ n += scnprintf(obp + n, len - n, " mmap_sz=%d\n", fp->mmap_sz);
n += scnprintf(obp + n, len - n,
" submitted=%d waiting=%d open thr_id=%d\n",
atomic_read(&fp->submitted),
--
2.25.1