| Message ID | 20221223092703.61927-3-hch@lst.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [1/2] Revert "remoteproc: qcom_q6v5_mss: map/unmap metadata region before/after use" | expand |
On Fri, Dec 23, 2022 at 10:27:03AM +0100, Christoph Hellwig wrote: > VM_FLUSH_RESET_PERMS is just for use with vmalloc as it is tied to freeing > the underlying pages. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > mm/vmalloc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 9e30f0b3920325..88a644cde9fb12 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2849,6 +2849,9 @@ void *vmap(struct page **pages, unsigned int count, > > might_sleep(); > > + if (WARN_ON_ONCE(flags & VM_FLUSH_RESET_PERMS)) > + return NULL; > + Might it be worth adding a specific vmap mask that explicitly indicates what flags are permissible on vmap()? Then this could become e.g.:- if (WARN_ON_ONCE(flags & ~VM_VMAP_PERMITTED_MASK)) return NULL; And would be self-documenting as to why we are disallowing flags (i.e. they are not part of the permitted vmap mask).
On Fri, Dec 23, 2022 at 10:24:25AM +0000, Lorenzo Stoakes wrote: > Might it be worth adding a specific vmap mask that explicitly indicates what > flags are permissible on vmap()? Then this could become e.g.:- > > if (WARN_ON_ONCE(flags & ~VM_VMAP_PERMITTED_MASK)) > return NULL; > > And would be self-documenting as to why we are disallowing flags (i.e. they are > not part of the permitted vmap mask). That's probably a good idea. It might need some time to audit for use of all the flags, though.
On Fri, Dec 23, 2022 at 03:03:12PM +0100, Christoph Hellwig wrote: > On Fri, Dec 23, 2022 at 10:24:25AM +0000, Lorenzo Stoakes wrote: > > Might it be worth adding a specific vmap mask that explicitly indicates what > > flags are permissible on vmap()? Then this could become e.g.:- > > > > if (WARN_ON_ONCE(flags & ~VM_VMAP_PERMITTED_MASK)) > > return NULL; > > > > And would be self-documenting as to why we are disallowing flags (i.e. they are > > not part of the permitted vmap mask). > > That's probably a good idea. It might need some time to audit > for use of all the flags, though. Perhaps leave that for a later patch (I could take a look as well), but in the meantime might be worth adding a quick comment here indicating why the flag is prohibited?
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 9e30f0b3920325..88a644cde9fb12 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2849,6 +2849,9 @@ void *vmap(struct page **pages, unsigned int count, might_sleep(); + if (WARN_ON_ONCE(flags & VM_FLUSH_RESET_PERMS)) + return NULL; + /* * Your top guard is someone else's bottom guard. Not having a top * guard compromises someone else's mappings too.
VM_FLUSH_RESET_PERMS is just for use with vmalloc as it is tied to freeing the underlying pages. Signed-off-by: Christoph Hellwig <hch@lst.de> --- mm/vmalloc.c | 3 +++ 1 file changed, 3 insertions(+)