* [PATCH] xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero()
@ 2019-07-30 18:34 Souptick Joarder
2019-07-30 19:56 ` Boris Ostrovsky
2019-07-31 6:15 ` Juergen Gross
0 siblings, 2 replies; 3+ messages in thread
From: Souptick Joarder @ 2019-07-30 18:34 UTC (permalink / raw)
To: boris.ostrovsky, jgross, sstabellini, marmarek
Cc: willy, akpm, linux, linux-mm, xen-devel, linux-kernel, stable,
gregkh, Souptick Joarder
'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
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero()
2019-07-30 18:34 [PATCH] xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero() Souptick Joarder
@ 2019-07-30 19:56 ` Boris Ostrovsky
2019-07-31 6:15 ` Juergen Gross
1 sibling, 0 replies; 3+ messages in thread
From: Boris Ostrovsky @ 2019-07-30 19:56 UTC (permalink / raw)
To: Souptick Joarder, jgross, sstabellini, marmarek
Cc: willy, akpm, linux, linux-mm, xen-devel, linux-kernel, stable, gregkh
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 {
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero()
2019-07-30 18:34 [PATCH] xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero() Souptick Joarder
2019-07-30 19:56 ` Boris Ostrovsky
@ 2019-07-31 6:15 ` Juergen Gross
1 sibling, 0 replies; 3+ messages in thread
From: Juergen Gross @ 2019-07-31 6:15 UTC (permalink / raw)
To: Souptick Joarder, marmarek, sstabellini, boris.ostrovsky
Cc: linux, willy, linux-mm, akpm, gregkh, xen-devel, linux-kernel, stable
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-07-30 18:34 [PATCH] xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero() Souptick Joarder
2019-07-30 19:56 ` Boris Ostrovsky
2019-07-31 6:15 ` Juergen Gross
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