[PATCH v7 0/7] arm_ffa, KVM: Fix FF-A emad offset calculations

[PATCH v7 0/7] arm_ffa, KVM: Fix FF-A emad offset calculations

[Sebastian Ene]

Hi all,

This series fixes the Endpoint Memory Access Descriptor (EMAD) offset
calculations and adds the necessary bounds checks for both the core
FF-A driver and the pKVM hypervisor.

Prior to FF-A version 1.1, the memory region header didn't specify an
explicit offset for the EMADs, leading to the assumption that they
immediately follow the header.
However, from v1.1 onwards, the specification dictates using the
ep_mem_offset` field to determine the start of the memory access
array.

The patches in this series address this by:
1. Updating the core `arm_ffa` firmware driver to correctly calculate
the descriptor
   offset using `ep_mem_offset` rather than defaulting to `sizeof(struct
ffa_mem_region)`.
   It also introduces bounds checking against `max_fragsize`.
2. Enhancing the pKVM hypervisor validation logic to no longer strictly
enforce that
   the descriptor strictly follows the header, aligning it with the
driver behavior
   and the FF-A specification, while also ensuring the offset falls
within the mailbox
   buffer bounds.

While addressing these bugs, Sashiko uncovered other issues that were
fixed in the same series.

All the patches aside from the first one in optee are urgent fixes as
they either impact the hypervisor security or kernel stability.

Changelog
#########
v6->v7:
- taking the patches from Mostafa and sending a new version with the
  collected tags
- Added overflow checks when doing `ep_offset + emad_size` in the arm
  ff-a driver
- Move the length check before the ffa_mem_reclaim
- fix compatibility break with ff-a version 1.0 reported by Sashiko
- add one more patch to fix an issue with the FFA_VERSION call
  that can lead to leaking pKVM stack un-initialized data to
  a host when -ftrivial-auto-var-init=zero is not used.

v5->v6:
- Add fixes tag
- Small clean up make variable declaration reverse christmas tree.

v4->v5:
- Collect Sudeep Rbs
- Add extra patch to check base address alignment.
- Remove WARN_ONs in KVM code
- Use ffa_emad_size_get() instead of hardcoded size in KVM code.

v3 -> v4:
- Address review comments and fix Sashiko bugs

v2 -> v3:
- Fixed typo in nvhe/ffa.c (missing sizeof)

v1 -> v2:
- For pKVM, removed the strict placement enforcement for `ep_mem_offset`
  as it is not
  compliant with the spec, and avoids making assumptions about the
driver's memory
  layout.

Link to:
########
v6:
https://lore.kernel.org/all/20260527150236.1978655-1-smostafa@google.com/
v5:
https://lore.kernel.org/all/20260526151934.3783707-1-smostafa@google.com/
v4:
https://lore.kernel.org/all/20260520204948.2440882-1-smostafa@google.com/
v3:
https://lore.kernel.org/all/20260512124442.1899107-1-sebastianene@google.com/
v2:
https://lore.kernel.org/all/20260430160241.1934777-1-sebastianene@google.com/
v1: https://lore.kernel.org/all/ae9KN9nkOgDYJcGP@google.com/T/#t

Mostafa Saleh (4):
  optee: ffa: Add NULL check in optee_ffa_lend_protmem
  firmware: arm_ffa: Fix out-of-bound writes in ffa_setup_and_transmit()
  KVM: arm64: Fix bounds checking in do_ffa_mem_reclaim()
  KVM: arm64: Ensure FFA ranges are page aligned

Sebastian Ene (3):
  firmware: arm_ffa: Fix Endpoint Memory Access Descriptor offset
    calculation
  KVM: arm64: Validate the offset to the mem access descriptor
  KVM: arm64: Zero out the stack initialized data in the FFA handler

 arch/arm64/kvm/hyp/nvhe/ffa.c     | 47 ++++++++++++++++++++++---------
 drivers/firmware/arm_ffa/driver.c | 25 ++++++++++------
 drivers/tee/optee/ffa_abi.c       |  3 ++
 include/linux/arm_ffa.h           |  2 +-
 4 files changed, 54 insertions(+), 23 deletions(-)

-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH v7 1/7] optee: ffa: Add NULL check in optee_ffa_lend_protmem

[Sebastian Ene]

From: Mostafa Saleh <smostafa@google.com>

From: Mostafa Saleh <smostafa@google.com>

Sashiko (locally) reports a possible null dereference under memory
pressure due to the lack of validation of the allocated pointer.

Fix that by adding the missing check.

Fixes: 2b78d79cdf96 ("optee: FF-A: dynamic protected memory allocation")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
---
 drivers/tee/optee/ffa_abi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tee/optee/ffa_abi.c b/drivers/tee/optee/ffa_abi.c
index b4372fa268d0..633715b98625 100644
--- a/drivers/tee/optee/ffa_abi.c
+++ b/drivers/tee/optee/ffa_abi.c
@@ -698,6 +698,9 @@ static int optee_ffa_lend_protmem(struct optee *optee, struct tee_shm *protmem,
 	int rc;
 
 	mem_attr = kzalloc_objs(*mem_attr, ma_count);
+	if (!mem_attr)
+		return -ENOMEM;
+
 	for (n = 0; n < ma_count; n++) {
 		mem_attr[n].receiver = mem_attrs[n] & U16_MAX;
 		mem_attr[n].attrs = mem_attrs[n] >> 16;
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH v7 2/7] firmware: arm_ffa: Fix out-of-bound writes in ffa_setup_and_transmit()

[Sebastian Ene]

From: Mostafa Saleh <smostafa@google.com>

From: Mostafa Saleh <smostafa@google.com>

Sashiko (locally) reports multiple out-of-bound issues in
ffa_setup_and_transmit:
1) Writing ep_mem_access->reserved can write out of bounds for FFA
   versions < 1.2 as ffa_emad_size_get() returns 16 bytes in that case
   while reserved has an offset of 24.
   Instead of zeroing fields, memset the struct to zero first based on
   the FFA version.

2) Make sure there is enough size to write constituents.

While at it, convert the only sizeof() in the driver that uses a
type instead of variable.

Reviewed-by: Sudeep Holla <sudeep.holla@kernel.org>
Fixes: 111a833dc5cb ("firmware: arm_ffa: Set reserved/MBZ fields to zero in the memory descriptors")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
 drivers/firmware/arm_ffa/driver.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index b9f17fda7243..059e2aae7ca0 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -715,11 +715,10 @@ ffa_setup_and_transmit(u32 func_id, void *buffer, u32 max_fragsize,
 	for (idx = 0; idx < args->nattrs; idx++) {
 		ep_mem_access = buffer +
 			ffa_mem_desc_offset(buffer, idx, drv_info->version);
+		memset(ep_mem_access, 0, ffa_emad_size_get(drv_info->version));
 		ep_mem_access->receiver = args->attrs[idx].receiver;
 		ep_mem_access->attrs = args->attrs[idx].attrs;
 		ep_mem_access->composite_off = composite_offset;
-		ep_mem_access->flag = 0;
-		ep_mem_access->reserved = 0;
 		ffa_emad_impdef_value_init(drv_info->version,
 					   ep_mem_access->impdef_val,
 					   args->attrs[idx].impdef_val);
@@ -759,7 +758,7 @@ ffa_setup_and_transmit(u32 func_id, void *buffer, u32 max_fragsize,
 			constituents = buffer;
 		}
 
-		if ((void *)constituents - buffer > max_fragsize) {
+		if ((void *)constituents + sizeof(*constituents) - buffer > max_fragsize) {
 			pr_err("Memory Region Fragment > Tx Buffer size\n");
 			return -EFAULT;
 		}
@@ -768,7 +767,7 @@ ffa_setup_and_transmit(u32 func_id, void *buffer, u32 max_fragsize,
 		constituents->pg_cnt = args->sg->length / FFA_PAGE_SIZE;
 		constituents->reserved = 0;
 		constituents++;
-		frag_len += sizeof(struct ffa_mem_region_addr_range);
+		frag_len += sizeof(*constituents);
 	} while ((args->sg = sg_next(args->sg)));
 
 	return ffa_transmit_fragment(func_id, addr, buf_sz, frag_len,
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH v7 3/7] firmware: arm_ffa: Fix Endpoint Memory Access Descriptor offset calculation

[Sebastian Ene]

Use the descriptor's `ep_mem_offset` to calculate the start of the endpoint
memory access array and to comply with the FF-A spec instead of defaulting
to `sizeof(struct ffa_mem_region)`.
This requires moving `ffa_mem_region_additional_setup()` earlier in the setup
flow.
Also, add sanity checks to ensure the calculated descriptor offsets do not
exceed `max_fragsize`.

Fixes: 113580530ee7 ("firmware: arm_ffa: Update memory descriptor to support v1.1 format")
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Reviewed-by: Sudeep Holla <sudeep.holla@kernel.org>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 drivers/firmware/arm_ffa/driver.c | 20 +++++++++++++++-----
 include/linux/arm_ffa.h           |  2 +-
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 059e2aae7ca0..92edf397bcd2 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -703,19 +703,30 @@ ffa_setup_and_transmit(u32 func_id, void *buffer, u32 max_fragsize,
 	struct ffa_composite_mem_region *composite;
 	struct ffa_mem_region_addr_range *constituents;
 	struct ffa_mem_region_attributes *ep_mem_access;
-	u32 idx, frag_len, length, buf_sz = 0, num_entries = sg_nents(args->sg);
+	u32 idx, frag_len, length, buf_sz = 0, num_entries = sg_nents(args->sg), ep_offset;
+	u32 emad_end, emad_size = ffa_emad_size_get(drv_info->version);
 
 	mem_region->tag = args->tag;
 	mem_region->flags = args->flags;
 	mem_region->sender_id = drv_info->vm_id;
 	mem_region->attributes = ffa_memory_attributes_get(func_id);
+
+	ffa_mem_region_additional_setup(drv_info->version, mem_region);
 	composite_offset = ffa_mem_desc_offset(buffer, args->nattrs,
 					       drv_info->version);
+	if (composite_offset + sizeof(*composite) > max_fragsize)
+		return -ENXIO;
 
 	for (idx = 0; idx < args->nattrs; idx++) {
-		ep_mem_access = buffer +
-			ffa_mem_desc_offset(buffer, idx, drv_info->version);
-		memset(ep_mem_access, 0, ffa_emad_size_get(drv_info->version));
+		ep_offset = ffa_mem_desc_offset(buffer, idx, drv_info->version);
+		if (check_add_overflow(ep_offset, emad_size, &emad_end))
+			return -ENXIO;
+
+		if (emad_end > max_fragsize)
+			return -ENXIO;
+
+		ep_mem_access = buffer + ep_offset;
+		memset(ep_mem_access, 0, emad_size);
 		ep_mem_access->receiver = args->attrs[idx].receiver;
 		ep_mem_access->attrs = args->attrs[idx].attrs;
 		ep_mem_access->composite_off = composite_offset;
@@ -725,7 +736,6 @@ ffa_setup_and_transmit(u32 func_id, void *buffer, u32 max_fragsize,
 	}
 	mem_region->handle = 0;
 	mem_region->ep_count = args->nattrs;
-	ffa_mem_region_additional_setup(drv_info->version, mem_region);
 
 	composite = buffer + composite_offset;
 	composite->total_pg_cnt = ffa_get_num_pages_sg(args->sg);
diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
index 81e603839c4a..62d67dae8b70 100644
--- a/include/linux/arm_ffa.h
+++ b/include/linux/arm_ffa.h
@@ -445,7 +445,7 @@ ffa_mem_desc_offset(struct ffa_mem_region *buf, int count, u32 ffa_version)
 	if (!FFA_MEM_REGION_HAS_EP_MEM_OFFSET(ffa_version))
 		offset += offsetof(struct ffa_mem_region, ep_mem_offset);
 	else
-		offset += sizeof(struct ffa_mem_region);
+		offset += buf->ep_mem_offset;
 
 	return offset;
 }
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH v7 4/7] KVM: arm64: Fix bounds checking in do_ffa_mem_reclaim()

[Sebastian Ene]

From: Mostafa Saleh <smostafa@google.com>

Sashiko (locally) reports out of bound write possiblity if SPMD
returns an invalid data.

While SPMD is considered trusted, pKVM does some basic checks,
for offset to be less than or equal len.

However, that is incorrect as even if the offset is smaller than
len pKVM can still access out of bound memory in the next
ffa_host_unshare_ranges().

Split this check into 2:
1- Check that the fixed portion of the descriptor fits.
2- After getting reg, check the variable array size addr_range_cnt
   fits.

Also, drop the WARN_ONs as that will panic the kernel and in the
next checks there are no WARNs, so that makes it consistent.

Fixes: 0a9f15fd5674 ("KVM: arm64: pkvm: Add support for fragmented FF-A descriptors")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 1af722771178..2d211661952e 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -607,8 +607,8 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
 	 * check that we end up with something that doesn't look _completely_
 	 * bogus.
 	 */
-	if (WARN_ON(offset > len ||
-		    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)) {
+	if (offset + CONSTITUENTS_OFFSET(0) > len ||
+	    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
 		ret = FFA_RET_ABORTED;
 		ffa_rx_release(res);
 		goto out_unlock;
@@ -636,11 +636,17 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
 		ffa_rx_release(res);
 	}
 
+	reg = (void *)buf + offset;
+	if (offset + CONSTITUENTS_OFFSET(reg->addr_range_cnt) > len) {
+		ret = FFA_RET_ABORTED;
+		ffa_rx_release(res);
+		goto out_unlock;
+	}
+
 	ffa_mem_reclaim(res, handle_lo, handle_hi, flags);
 	if (res->a0 != FFA_SUCCESS)
 		goto out_unlock;
 
-	reg = (void *)buf + offset;
 	/* If the SPMD was happy, then we should be too. */
 	WARN_ON(ffa_host_unshare_ranges(reg->constituents,
 					reg->addr_range_cnt));
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH v7 5/7] KVM: arm64: Validate the offset to the mem access descriptor

[Sebastian Ene]

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: 42fb33dde42b ("KVM: arm64: Use FF-A 1.1 with pKVM")
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 2d211661952e..1a2abd0154c6 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -476,11 +476,14 @@ 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_HAS_EP_MEM_OFFSET(hyp_ffa_version) ?
+		offsetof(struct ffa_mem_region, ep_mem_offset) :
+		sizeof(struct ffa_mem_region);
 
 	if (addr_mbz || npages_mbz || fraglen > len ||
 	    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
@@ -488,8 +491,7 @@ 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 +510,13 @@ 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 +581,9 @@ 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 +606,14 @@ 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
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH v7 6/7] KVM: arm64: Ensure FFA ranges are page aligned

[Sebastian Ene]

From: Mostafa Saleh <smostafa@google.com>

At the moment we only check that the size of the range is page
aligned, and truncate the address to the page boundary.
This make an assumption that TZ will do the same.

However, it might decide to use the extra offset of the neighbour
page at the end, which is valid under FFA if NS is using larger
page size.

Harden this check by also checking that the base address is aligned
and reject it otherwise.

Fixes: 436090001776 ("KVM: arm64: Handle FFA_MEM_SHARE calls from the host")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 1a2abd0154c6..d7c5701d0584 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -352,7 +352,7 @@ static u32 __ffa_host_share_ranges(struct ffa_mem_region_addr_range *ranges,
 		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
 		u64 pfn = hyp_phys_to_pfn(range->address);
 
-		if (!PAGE_ALIGNED(sz))
+		if (!PAGE_ALIGNED(sz | range->address))
 			break;
 
 		if (__pkvm_host_share_ffa(pfn, sz / PAGE_SIZE))
@@ -372,7 +372,7 @@ static u32 __ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
 		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
 		u64 pfn = hyp_phys_to_pfn(range->address);
 
-		if (!PAGE_ALIGNED(sz))
+		if (!PAGE_ALIGNED(sz | range->address))
 			break;
 
 		if (__pkvm_host_unshare_ffa(pfn, sz / PAGE_SIZE))
-- 
2.54.0.1136.gdb2ca164c4-goog

[PATCH v7 7/7] KVM: arm64: Zero out the stack initialized data in the FFA handler

[Sebastian Ene]

Don't leak hypervisor stack data when using the FFA_VERSION call.
When the compiler doesn't support -ftrivial-auto-var-init=zero option
we need to zero out the stack initialized variable before returning data
to the host caller.

Reported-by: Sashiko AI <sashiko-bot@kernel.org>
Closes:
https://lore.kernel.org/all/20260616160016.C62C81F000E9@smtp.kernel.org/
Fixes: c9c012625e12 ("KVM: arm64: Trap FFA_VERSION host call in pKVM")
Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index d7c5701d0584..b321682ead04 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -883,7 +883,7 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
 
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 {
-	struct arm_smccc_1_2_regs res;
+	struct arm_smccc_1_2_regs res = {0};
 
 	/*
 	 * There's no way we can tell what a non-standard SMC call might
-- 
2.54.0.1136.gdb2ca164c4-goog

Re: [PATCH v7 4/7] KVM: arm64: Fix bounds checking in do_ffa_mem_reclaim()

[Vincent Donnefort]

On Wed, Jun 17, 2026 at 02:51:27PM +0000, Sebastian Ene wrote:
> From: Mostafa Saleh <smostafa@google.com>
> 
> Sashiko (locally) reports out of bound write possiblity if SPMD
> returns an invalid data.
> 
> While SPMD is considered trusted, pKVM does some basic checks,
> for offset to be less than or equal len.
> 
> However, that is incorrect as even if the offset is smaller than
> len pKVM can still access out of bound memory in the next
> ffa_host_unshare_ranges().
> 
> Split this check into 2:
> 1- Check that the fixed portion of the descriptor fits.
> 2- After getting reg, check the variable array size addr_range_cnt
>    fits.
> 
> Also, drop the WARN_ONs as that will panic the kernel and in the
> next checks there are no WARNs, so that makes it consistent.
> 
> Fixes: 0a9f15fd5674 ("KVM: arm64: pkvm: Add support for fragmented FF-A descriptors")
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> Signed-off-by: Sebastian Ene <sebastianene@google.com>

FTR, I believe the comment about composite_off in include/linux/arm_ffa.h is
incorrect. It is an offset to a ffa_composite_mem_region (not a
ffa_mem_region_addr_range)

Reviewed-by: Vincent Donnefort <vdonnefort@google.com>

> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 1af722771178..2d211661952e 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -607,8 +607,8 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
>  	 * check that we end up with something that doesn't look _completely_
>  	 * bogus.
>  	 */
> -	if (WARN_ON(offset > len ||
> -		    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)) {
> +	if (offset + CONSTITUENTS_OFFSET(0) > len ||
> +	    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
>  		ret = FFA_RET_ABORTED;
>  		ffa_rx_release(res);
>  		goto out_unlock;
> @@ -636,11 +636,17 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
>  		ffa_rx_release(res);
>  	}
>  
> +	reg = (void *)buf + offset;
> +	if (offset + CONSTITUENTS_OFFSET(reg->addr_range_cnt) > len) {
> +		ret = FFA_RET_ABORTED;
> +		ffa_rx_release(res);
> +		goto out_unlock;
> +	}
> +
>  	ffa_mem_reclaim(res, handle_lo, handle_hi, flags);
>  	if (res->a0 != FFA_SUCCESS)
>  		goto out_unlock;
>  
> -	reg = (void *)buf + offset;
>  	/* If the SPMD was happy, then we should be too. */
>  	WARN_ON(ffa_host_unshare_ranges(reg->constituents,
>  					reg->addr_range_cnt));
> -- 
> 2.54.0.1136.gdb2ca164c4-goog
> 

Re: [PATCH v7 5/7] KVM: arm64: Validate the offset to the mem access descriptor

[Vincent Donnefort]

On Wed, Jun 17, 2026 at 02:51:28PM +0000, Sebastian Ene wrote:
> 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: 42fb33dde42b ("KVM: arm64: Use FF-A 1.1 with pKVM")
> Signed-off-by: Sebastian Ene <sebastianene@google.com>
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 2d211661952e..1a2abd0154c6 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -476,11 +476,14 @@ 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_HAS_EP_MEM_OFFSET(hyp_ffa_version) ?
> +		offsetof(struct ffa_mem_region, ep_mem_offset) :
> +		sizeof(struct ffa_mem_region);
>  
>  	if (addr_mbz || npages_mbz || fraglen > len ||
>  	    fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) {
> @@ -488,8 +491,7 @@ 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)) {

Can't we replace mem_region_len with ffa_mem_desc_offset()? that pretty much
looks like the same thing.


>  		ret = FFA_RET_INVALID_PARAMETERS;
>  		goto out;
>  	}
> @@ -508,8 +510,13 @@ 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) {

This check looks like ffa_mem_desc_offset() with count to 1.


> +		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 +581,9 @@ 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 +606,14 @@ 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) {

ditto. ffa_mem_desc_offset()

> +		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
> -- 
> 2.54.0.1136.gdb2ca164c4-goog
> 

Re: [PATCH v7 6/7] KVM: arm64: Ensure FFA ranges are page aligned

[Vincent Donnefort]

On Wed, Jun 17, 2026 at 02:51:29PM +0000, Sebastian Ene wrote:
> From: Mostafa Saleh <smostafa@google.com>
> 
> At the moment we only check that the size of the range is page
> aligned, and truncate the address to the page boundary.
> This make an assumption that TZ will do the same.
> 
> However, it might decide to use the extra offset of the neighbour
> page at the end, which is valid under FFA if NS is using larger
> page size.

I failed to parse this 

But I see 

/* The base IPA of the constituent memory region, aligned to 4 kiB */ 

So it sounds fair to prevent oversharing when PAGE_SIZE > 4KiB

> 
> Harden this check by also checking that the base address is aligned
> and reject it otherwise.
> 
> Fixes: 436090001776 ("KVM: arm64: Handle FFA_MEM_SHARE calls from the host")
> Signed-off-by: Mostafa Saleh <smostafa@google.com>
> Signed-off-by: Sebastian Ene <sebastianene@google.com>

Perhaps the commit description needs some improvement.

The rest looks good.

Reviewed-by: Vincent Donnefort <vdonnefort@google.com>

> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 1a2abd0154c6..d7c5701d0584 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -352,7 +352,7 @@ static u32 __ffa_host_share_ranges(struct ffa_mem_region_addr_range *ranges,
>  		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
>  		u64 pfn = hyp_phys_to_pfn(range->address);
>  
> -		if (!PAGE_ALIGNED(sz))
> +		if (!PAGE_ALIGNED(sz | range->address))
>  			break;
>  
>  		if (__pkvm_host_share_ffa(pfn, sz / PAGE_SIZE))
> @@ -372,7 +372,7 @@ static u32 __ffa_host_unshare_ranges(struct ffa_mem_region_addr_range *ranges,
>  		u64 sz = (u64)range->pg_cnt * FFA_PAGE_SIZE;
>  		u64 pfn = hyp_phys_to_pfn(range->address);
>  
> -		if (!PAGE_ALIGNED(sz))
> +		if (!PAGE_ALIGNED(sz | range->address))
>  			break;
>  
>  		if (__pkvm_host_unshare_ffa(pfn, sz / PAGE_SIZE))
> -- 
> 2.54.0.1136.gdb2ca164c4-goog
> 

Re: [PATCH v7 7/7] KVM: arm64: Zero out the stack initialized data in the FFA handler

[Vincent Donnefort]

On Wed, Jun 17, 2026 at 02:51:30PM +0000, Sebastian Ene wrote:
> Don't leak hypervisor stack data when using the FFA_VERSION call.
> When the compiler doesn't support -ftrivial-auto-var-init=zero option

Even when it does, I believe this is an optional kernel option.

> we need to zero out the stack initialized variable before returning data
> to the host caller.
> 
> Reported-by: Sashiko AI <sashiko-bot@kernel.org>

It seems most people are using "Reported-by: Sashiko <sashiko-bot@kernel.org>"

> Closes:
> https://lore.kernel.org/all/20260616160016.C62C81F000E9@smtp.kernel.org/
> Fixes: c9c012625e12 ("KVM: arm64: Trap FFA_VERSION host call in pKVM")
> Signed-off-by: Sebastian Ene <sebastianene@google.com>

Reviewed-by: Vincent Donnefort <vdonnefort@google.com>

> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index d7c5701d0584..b321682ead04 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -883,7 +883,7 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
>  
>  bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
>  {
> -	struct arm_smccc_1_2_regs res;
> +	struct arm_smccc_1_2_regs res = {0};
>  
>  	/*
>  	 * There's no way we can tell what a non-standard SMC call might
> -- 
> 2.54.0.1136.gdb2ca164c4-goog
>