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Filename Latest commit message Latest commit date
Oleksandr Tyshchenko 5c03cad51b xen/arm: Fix race in RB-tree based P2M accounting
commit b75cd218274e01d026dc5240e86fdeb44bbed0c8 upstream.

During the PV driver life cycle the mappings are added to
the RB-tree by set_foreign_p2m_mapping(), which is called from
gnttab_map_refs() and are removed by clear_foreign_p2m_mapping()
which is called from gnttab_unmap_refs(). As both functions end
up calling __set_phys_to_machine_multi() which updates the RB-tree,
this function can be called concurrently.

There is already a "p2m_lock" to protect against concurrent accesses,
but the problem is that the first read of "phys_to_mach.rb_node"
in __set_phys_to_machine_multi() is not covered by it, so this might
lead to the incorrect mappings update (removing in our case) in RB-tree.

In my environment the related issue happens rarely and only when
PV net backend is running, the xen_add_phys_to_mach_entry() claims
that it cannot add new pfn <-> mfn mapping to the tree since it is
already exists which results in a failure when mapping foreign pages.

But there might be other bad consequences related to the non-protected
root reads such use-after-free, etc.

While at it, also fix the similar usage in __pfn_to_mfn(), so
initialize "struct rb_node *n" with the "p2m_lock" held in both
functions to avoid possible bad consequences.

This is CVE-2022-33744 / XSA-406.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-07-07 17:36:53 +02:00
arch xen/arm: Fix race in RB-tree based P2M accounting 2022-07-07 17:36:53 +02:00
block
certs
crypto
Documentation
drivers xen/blkfront: force data bouncing when backend is untrusted 2022-07-07 17:36:53 +02:00
fs
include linux/dim: Fix divide by 0 in RDMA DIM 2022-07-07 17:36:49 +02:00
init
ipc
kernel kexec_file: drop weak attribute from arch_kexec_apply_relocations[_add] 2022-07-02 16:28:50 +02:00
lib
LICENSES
mm
net ipv6/sit: fix ipip6_tunnel_get_prl return value 2022-07-07 17:36:51 +02:00
samples
scripts modpost: fix section mismatch check for exported init/exit sections 2022-06-29 08:58:49 +02:00
security
sound
tools selftests/rseq: Change type of rseq_offset to ptrdiff_t 2022-07-07 17:36:52 +02:00
usr
virt
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COPYING
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Makefile Linux 5.4.203 2022-07-02 16:28:53 +02:00
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