drivers/xen/gntdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
'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.
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>
---
drivers/xen/gntdev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 4c339c7..a446a72 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 {
--
1.9.1
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On 7/30/19 2:34 PM, Souptick Joarder wrote: > '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> > --- > drivers/xen/gntdev.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index 4c339c7..a446a72 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 { _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
On 30.07.19 20:34, Souptick Joarder wrote: > '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. > > 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> Pushed to xen/tip.git for-linus-5.3a Juergen _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
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