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KVM: arm64: Validate the offset to the mem access descriptor

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Prevent the pKVM hypervisor from making assumptions that the
endpoint memory access descriptor (EMAD) comes right after the
FF-A memory region header.
Prior to FF-A version 1.1 the header of the memory region
didn't contain an offset to the endpoint memory access descriptor.
The layout of a memory transaction looks like this from 1.1 onward:
Type | Field name | Offset
[ Header | ffa_mem_region  | 0
  EMAD 1 | ffa_mem_region_attributes) | ffa_mem_region.ep_mem_offset
]
Verify that the offset to the first endpoint memory access descriptor
is within the mailbox buffer bounds.

Also, fix one hardcoded sizeof(struct ffa_mem_region_attributes) that
should be replaced ffa_emad_size_get() for compatibility with FFA v1.0.

Fixes: 42fb33dde4 ("KVM: arm64: Use FF-A 1.1 with pKVM")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Link: https://patch.msgid.link/20260702103848.1647249-5-sebastianene@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Sebastian Ene 2026-07-02 10:38:41 +00:00 committed by Marc Zyngier
parent 8c6db30d79
commit a6b49d27c1
2 changed files with 26 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
arch/arm64/kvm/hyp/nvhe/ffa.c
View File

@ -476,11 +476,12 @@ static void __do_ffa_mem_xfer(const u64 func_id,
DECLARE_REG(u32, fraglen, ctxt, 2);
DECLARE_REG(u64, addr_mbz, ctxt, 3);
DECLARE_REG(u32, npages_mbz, ctxt, 4);
u32 offset, nr_ranges, checked_offset, em_mem_access_off;
struct ffa_mem_region_attributes *ep_mem_access;
struct ffa_composite_mem_region *reg;
struct ffa_mem_region *buf;
u32 offset, nr_ranges, checked_offset;
int ret = 0;
size_t mem_region_len = FFA_MEM_REGION_SZ(hyp_ffa_version);
if (addr_mbz || npages_mbz || fraglen > len ||
fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
@ -488,8 +489,7 @@ static void __do_ffa_mem_xfer(const u64 func_id,
goto out;
}
if (fraglen < sizeof(struct ffa_mem_region) +
sizeof(struct ffa_mem_region_attributes)) {
if (fraglen < mem_region_len + ffa_emad_size_get(hyp_ffa_version)) {
ret = FFA_RET_INVALID_PARAMETERS;
goto out;
}
@ -508,8 +508,13 @@ static void __do_ffa_mem_xfer(const u64 func_id,
buf = hyp_buffers.tx;
memcpy(buf, host_buffers.tx, fraglen);
ep_mem_access = (void *)buf +
ffa_mem_desc_offset(buf, 0, hyp_ffa_version);
em_mem_access_off = ffa_mem_desc_offset(buf, 0, hyp_ffa_version);
if ((u64)em_mem_access_off + ffa_emad_size_get(hyp_ffa_version) > fraglen) {
ret = FFA_RET_INVALID_PARAMETERS;
goto out_unlock;
}
ep_mem_access = (void *)buf + em_mem_access_off;
offset = ep_mem_access->composite_off;
if (!offset || buf->ep_count != 1 || buf->sender_id != HOST_FFA_ID) {
ret = FFA_RET_INVALID_PARAMETERS;
@ -574,9 +579,9 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
DECLARE_REG(u32, handle_lo, ctxt, 1);
DECLARE_REG(u32, handle_hi, ctxt, 2);
DECLARE_REG(u32, flags, ctxt, 3);
u32 offset, len, fraglen, fragoff, em_mem_access_off;
struct ffa_mem_region_attributes *ep_mem_access;
struct ffa_composite_mem_region *reg;
u32 offset, len, fraglen, fragoff;
struct ffa_mem_region *buf;
int ret = 0;
u64 handle;
@ -599,8 +604,14 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
len = res->a1;
fraglen = res->a2;
ep_mem_access = (void *)buf +
ffa_mem_desc_offset(buf, 0, hyp_ffa_version);
em_mem_access_off = ffa_mem_desc_offset(buf, 0, hyp_ffa_version);
if ((u64)em_mem_access_off + ffa_emad_size_get(hyp_ffa_version) > fraglen) {
ret = FFA_RET_INVALID_PARAMETERS;
ffa_rx_release(res);
goto out_unlock;
}
ep_mem_access = (void *)buf + em_mem_access_off;
offset = ep_mem_access->composite_off;
/*
* We can trust the SPMD to get this right, but let's at least

7
include/linux/arm_ffa.h
View File

@ -421,6 +421,13 @@ struct ffa_mem_region {
#define FFA_EMAD_HAS_IMPDEF_FIELD(version) ((version) >= FFA_VERSION_1_2)
#define FFA_MEM_REGION_HAS_EP_MEM_OFFSET(version) ((version) > FFA_VERSION_1_0)
/* The layout changed from FFA_VERSION_1_0 and the region includes an
* ep_mem_offset.
*/
#define FFA_MEM_REGION_SZ(version) (!FFA_MEM_REGION_HAS_EP_MEM_OFFSET((version)) ?\
offsetof(struct ffa_mem_region, ep_mem_offset) :\
sizeof(struct ffa_mem_region))
static inline u32 ffa_emad_size_get(u32 ffa_version)
{
u32 sz;