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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Shinichiro Kawasaki Subject: Re: [PATCH mm-hotfixes] mm/vma: remove __vma_check_mmap_hook() Message-ID: References: <20260413105713.92625-1-ljs@kernel.org> <20260413221724.c939e483e83304fb40e3d6da@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260413221724.c939e483e83304fb40e3d6da@linux-foundation.org> X-Rspam-User: X-Stat-Signature: txcb4zmxiutwb3qta88u7yhz8hfxmxbx X-Rspamd-Queue-Id: 2EFD3180004 X-Rspamd-Server: rspam09 X-HE-Tag: 1776234905-911096 X-HE-Meta: U2FsdGVkX19J2EcenlE/veZiz+wfualOmPrPncTFYHZdqliyS87E9hJZ+/2V/PR7KqjlUpButWAOXzcjx3UAm0V2DDhA+TKD1rllCBf805x2pdX8VREgVWkudsKxBgwj50xOUMjSjX6mebIB/deEdXA1lJNuw681ChS+Px4kmUlAnkj+3HqOXnWFVfSQ8sn5Ckz6G/gpawdNW4Mo0g7/DSFLuNZM12kTmRweesnQs2o6Vu85G2hKDFO0QvQdCYB4A6q6tcL+1a4mzMmJM3gkaIooYdvOdserbekHXX7Iktf9EDQ64O7u9+IftiL7LIi1X3uEXoeGUbdwdCcLcEE+BjbGoy1MRSPlPSXHTjl0Y+425/ZHvgCwzy0rMcWiVW043eRqLfgVQFR2i/24VC4QL1ziALDSF5G7fcb8ck6K8jXmfCrDlDJQzdbWy1aXnqYHEg1nKf/I7a21bAyTW/cUhVB4JiOMYBkPilOJG0knC7MIcHECB0K86KnyDQHcFzj5OEZKwn74Hhi7GN8zwOP6YHOb5e8gsff2bxL+KHvygOA+mlX8dbLYfQgtR+/WVWPWg4tPAOezL7U+Ii1TOWvsBfchY5C3ghEklggrvajJHgWfoU61y4sYtMFl7ydMxB7Nbyd0wE3oj0yCUPmPEheyYELUtu28j336tWvlYHlvnUIZFu1gKakUWOHDcInNl8JAOU1hSlRVxvQaskG3JHjZVxW8aXrxm/pHgESMoHRVyOFAvWsmVe/nsA07ARUt6EJ/4/f1LoXWGbgNfMxGD4yfkUG063uT0jQObvO2z1wKIi57oStajNsfcbvW5gmGmQU6BkRgWret26MDhfEhJThoGJvnsM03KAYtbnQy4RmlKAnKF+6JBpmjW6MU4KxRvKpc94J0i+fIfewh1iWesjaOdtUZfNyzu+LAoXvDuhgmrkSFMdqUkCRsOfwtYcd9qUARSJ82dAIOKCAzlKOlY85 8pmcXBqr yrs6psQ550FuIfRpthW3Y0uHzHxSv3iKhqCLEgavR9dmpreKX/IkzK0EzgSkLXc1PxgpF8JEilYW5DkWEkPHdvYCM7aNUc5B8qWljfkwNysJOMe4xGcArNubIAxqGYKRnjm4u6a0NaKA9Z8gQn2ZvDkVTfUSdGQo6lVkDScg1qYnI8Ov1jwB8C6Ql1l1pY8885iCV5THpZT663S1fRylFozAY4U9Y+Wx0mOnd/eOvRnvqc7KFEDnGBtqJwKXi7Bh6d4oMEcXP/jX10V3MBrbM5SMWQ6Nr5CuWBrfIA/8R9WDxkjFkVGAx675vloNWmhdv1aWm Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 13, 2026 at 10:17:24PM -0700, Andrew Morton wrote: > On Mon, 13 Apr 2026 11:57:13 +0100 Lorenzo Stoakes wrote: > > > Commit c50ca15dd496 ("mm: add vm_ops->mapped hook") introduced > > __vma_check_mmap_hook() in order to assert that a driver doesn't > > incorrectly implement both an f_op->mmap() and a vm_ops->mapped hook, the > > latter of which would not ultimately get invoked. > > > > However, this did not correctly account for stacked drivers (or drivers > > that otherwise use the compatibility layer) which might recursively call > > an mmap_prepare hook via the compatibility layer. > > > > Thus the nested mmap_prepare() invocation might result in a VMA which has > > vm_ops->mapped set with an overlaying mmap() hook, causing the > > __vma_check_mmap_hook() to fail in vfs_mmap(), wrongly failing the > > operation. > > > > This patch resolves this by simply removing the check, as we can't be > > certain that an mmap() hook doesn't at some point invoke the compatibility > > layer, and it's not worth trying to track it. > > Cool, thanks. > > > Fixes: c50ca15dd496 ("mm: add vm_ops->mapped hook") > > That's presently in flight mm.git->Linus, So I'll include this fix in > next week's second batch of MM updates into Linus. Ack thanks! > > > > c50ca15dd496 is in mm-stable, so thought best to do as fix-patch? Will > > leave a small bisection hazard (unfortunately) so putting this as close as > > possible to the patch it fixes would be ideal. > > Yep, I did that. Thanks! > > Cheers, Lorenzo