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| author | Souptick Joarder <jrdr.linux@gmail.com> | 2019-07-31 00:04:56 +0530 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2019-07-31 08:13:59 +0200 |
| commit | 8d1502f629c9966743de45744f4c1ba93a57d105 (patch) | |
| tree | c66286cbeaca35ca3424d1343d17edfd89e437a7 /drivers | |
| parent | 09e088a4903bd0dd911b4f1732b250130cdaffed (diff) | |
| download | linux-8d1502f629c9966743de45744f4c1ba93a57d105.tar.bz2 | |
xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero()
'commit df9bde015a72 ("xen/gntdev.c: convert to use vm_map_pages()")'
breaks gntdev driver. If vma->vm_pgoff > 0, vm_map_pages()
will:
- use map->pages starting at vma->vm_pgoff instead of 0
- verify map->count against vma_pages()+vma->vm_pgoff instead of just
vma_pages().
In practice, this breaks using a single gntdev FD for mapping multiple
grants.
relevant strace output:
[pid 857] ioctl(7, IOCTL_GNTDEV_MAP_GRANT_REF, 0x7ffd3407b6d0) = 0
[pid 857] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 7, 0) =
0x777f1211b000
[pid 857] ioctl(7, IOCTL_GNTDEV_SET_UNMAP_NOTIFY, 0x7ffd3407b710) = 0
[pid 857] ioctl(7, IOCTL_GNTDEV_MAP_GRANT_REF, 0x7ffd3407b6d0) = 0
[pid 857] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 7,
0x1000) = -1 ENXIO (No such device or address)
details here:
https://github.com/QubesOS/qubes-issues/issues/5199
The reason is -> ( copying Marek's word from discussion)
vma->vm_pgoff is used as index passed to gntdev_find_map_index. It's
basically using this parameter for "which grant reference to map".
map struct returned by gntdev_find_map_index() describes just the pages
to be mapped. Specifically map->pages[0] should be mapped at
vma->vm_start, not vma->vm_start+vma->vm_pgoff*PAGE_SIZE.
When trying to map grant with index (aka vma->vm_pgoff) > 1,
__vm_map_pages() will refuse to map it because it will expect map->count
to be at least vma_pages(vma)+vma->vm_pgoff, while it is exactly
vma_pages(vma).
Converting vm_map_pages() to use vm_map_pages_zero() will fix the
problem.
Marek has tested and confirmed the same.
Cc: stable@vger.kernel.org # v5.2+
Fixes: df9bde015a72 ("xen/gntdev.c: convert to use vm_map_pages()")
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/xen/gntdev.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 4c339c7e66e5..a446a7221e13 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -1143,7 +1143,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) goto out_put_map; if (!use_ptemod) { - err = vm_map_pages(vma, map->pages, map->count); + err = vm_map_pages_zero(vma, map->pages, map->count); if (err) goto out_put_map; } else { |