On 21.02.25 17:07, Patrick Roy wrote:
Add AS_NO_DIRECT_MAP for mappings where direct map entries of folios are
set to not present . Currently, mappings that match this description are
secretmem mappings (memfd_secret()). Later, some guest_memfd
configurations will also fall into this category.
Reject this new type of mappings in all locations that currently reject
secretmem mappings, on the assumption that if secretmem mappings are
rejected somewhere, it is precisely because of an inability to deal with
folios without direct map entries.
Use a new flag instead of overloading AS_INACCESSIBLE (which is already
set by guest_memfd) because not all guest_memfd mappings will end up
being direct map removed (e.g. in pKVM setups, parts of guest_memfd that
can be mapped to userspace should also be GUP-able, and generally not
have restrictions on who can access it).
Signed-off-by: Patrick Roy <roypat@xxxxxxxxxxxx>
---
...
static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
{
return mapping->gfp_mask;
diff --git a/lib/buildid.c b/lib/buildid.c
index c4b0f376fb34..80b5d805067f 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -65,8 +65,8 @@ static int freader_get_folio(struct freader *r, loff_t file_off)
freader_put_folio(r);
- /* reject secretmem folios created with memfd_secret() */
- if (secretmem_mapping(r->file->f_mapping))
+ /* reject secretmem folios created with memfd_secret() or guest_memfd() */
+ if (secretmem_mapping(r->file->f_mapping) || mapping_no_direct_map(r->file->f_mapping))
return -EFAULT;
Maybe I'm missing it, but why do we have to special-case secretmem with
that at all anymore?
Couldn't we just let secretmem set AS_NO_DIRECT_MAP as well, and convert
all/most secretmem specific stuff to check AS_NO_DIRECT_MAP as well?
--
Cheers,
David / dhildenb
