drivers/xen/gntdev.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
The error paths of gntdev_mmap() can call unmap_grant_pages() even
though not all of the pages have been successfully mapped. This will
trigger the WARN_ON()s in __unmap_grant_pages_done(). The number of
warnings can be very large; I have observed thousands of lines of
warnings in the systemd journal.
Avoid this problem by only warning on unmapping failure if the handle
being unmapped is not INVALID_GRANT_HANDLE. The handle field of any
page that was not successfully mapped will be INVALID_GRANT_HANDLE, so
this catches all cases where unmapping can legitimately fail.
Suggested-by: Juergen Gross <jgross@suse.com>
Cc: stable@vger.kernel.org
Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()")
---
drivers/xen/gntdev.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 4b56c39f766d4da68570d08d963f6ef40c8d9c37..22fcd503f4a4487d0aed147c94f432683dad8c73 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -396,13 +396,17 @@ static void __unmap_grant_pages_done(int result,
unsigned int offset = data->unmap_ops - map->unmap_ops;
for (i = 0; i < data->count; i++) {
- WARN_ON(map->unmap_ops[offset+i].status);
+ WARN_ON(map->unmap_ops[offset+i].status &&
+ map->unmap_ops[offset+i].handle !=
+ INVALID_GRANT_HANDLE);
pr_debug("unmap handle=%d st=%d\n",
map->unmap_ops[offset+i].handle,
map->unmap_ops[offset+i].status);
map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
if (use_ptemod) {
- WARN_ON(map->kunmap_ops[offset+i].status);
+ WARN_ON(map->kunmap_ops[offset+i].status &&
+ map->kunmap_ops[offset+i].handle !=
+ INVALID_GRANT_HANDLE);
pr_debug("kunmap handle=%u st=%d\n",
map->kunmap_ops[offset+i].handle,
map->kunmap_ops[offset+i].status);
--
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
On 08.07.22 19:37, Demi Marie Obenour wrote: Hello Demi Marie Please add subsystem to the commit subject, for example "xen/gntdev:". > The error paths of gntdev_mmap() can call unmap_grant_pages() even > though not all of the pages have been successfully mapped. This will > trigger the WARN_ON()s in __unmap_grant_pages_done(). The number of > warnings can be very large; I have observed thousands of lines of > warnings in the systemd journal. > > Avoid this problem by only warning on unmapping failure if the handle > being unmapped is not INVALID_GRANT_HANDLE. The handle field of any > page that was not successfully mapped will be INVALID_GRANT_HANDLE, so > this catches all cases where unmapping can legitimately fail. > > Suggested-by: Juergen Gross <jgross@suse.com> > Cc: stable@vger.kernel.org > Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com> > Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()") > --- > drivers/xen/gntdev.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index 4b56c39f766d4da68570d08d963f6ef40c8d9c37..22fcd503f4a4487d0aed147c94f432683dad8c73 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -396,13 +396,17 @@ static void __unmap_grant_pages_done(int result, > unsigned int offset = data->unmap_ops - map->unmap_ops; > > for (i = 0; i < data->count; i++) { > - WARN_ON(map->unmap_ops[offset+i].status); > + WARN_ON(map->unmap_ops[offset+i].status && > + map->unmap_ops[offset+i].handle != > + INVALID_GRANT_HANDLE); Nit: While extending the check I would clarify the first half of it: "map->unmap_ops[offset+i].status != GNTST_okay" > pr_debug("unmap handle=%d st=%d\n", > map->unmap_ops[offset+i].handle, > map->unmap_ops[offset+i].status); > map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE; > if (use_ptemod) { > - WARN_ON(map->kunmap_ops[offset+i].status); > + WARN_ON(map->kunmap_ops[offset+i].status && > + map->kunmap_ops[offset+i].handle != > + INVALID_GRANT_HANDLE); ditto With updated subject: Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> > pr_debug("kunmap handle=%u st=%d\n", > map->kunmap_ops[offset+i].handle, > map->kunmap_ops[offset+i].status); -- Regards, Oleksandr Tyshchenko
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