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arm64: RSI: fix field-spanning write warning in attestation token init

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The challenge is passed in registers a1 through a8. However, copying to
&regs.a1 makes FORTIFY treat the destination as the single a1 field,
resulting in a field-spanning write warning. [1]

Overlay the SMCCC register structure with an RSI-specific argument
layout and copy the challenge into an explicit 64-byte array. This keeps
the existing a1-a8 argument encoding while giving the copy a correctly
sized destination object.

[1]
memcpy: detected field-spanning write (size 64) of single field "&regs.a1" at ./arch/arm64/include/asm/rsi_cmds.h:119 (size 8)
WARNING: ./arch/arm64/include/asm/rsi_cmds.h:119 at rsi_attestation_token_init+0xdc/0xf8 [arm_cca_guest], CPU#0: cat/3314

Fixes: b880a80011 ("arm64: rsi: Add RSI definitions")
Signed-off-by: Kohei Enju <enju.kohei@fujitsu.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Kohei Enju 2026-07-15 21:28:50 +09:00 committed by Will Deacon
parent ecc2e04686
commit 221049874b
1 changed files with 19 additions and 8 deletions
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27
arch/arm64/include/asm/rsi_cmds.h
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@ -88,6 +88,14 @@ static inline long rsi_set_addr_range_state(phys_addr_t start,
return res.a0;
}
#define RSI_ATTEST_CHALLENGE_MIN_SIZE 32
#define RSI_ATTEST_CHALLENGE_MAX_SIZE 64
struct rsi_attestation_token_init_args {
unsigned long fid;
u8 challenge[RSI_ATTEST_CHALLENGE_MAX_SIZE];
};
/**
* rsi_attestation_token_init - Initialise the operation to retrieve an
* attestation token.
@ -109,18 +117,21 @@ static inline long rsi_set_addr_range_state(phys_addr_t start,
static inline long
rsi_attestation_token_init(const u8 *challenge, unsigned long size)
{
struct arm_smccc_1_2_regs regs = { 0 };
union {
struct arm_smccc_1_2_regs regs;
struct rsi_attestation_token_init_args init;
} args = { 0 };
/* The challenge must be at least 32bytes and at most 64bytes */
if (!challenge || size < 32 || size > 64)
if (!challenge || size < RSI_ATTEST_CHALLENGE_MIN_SIZE ||
size > RSI_ATTEST_CHALLENGE_MAX_SIZE)
return -EINVAL;
regs.a0 = SMC_RSI_ATTESTATION_TOKEN_INIT;
memcpy(&regs.a1, challenge, size);
arm_smccc_1_2_smc(&regs, &regs);
args.init.fid = SMC_RSI_ATTESTATION_TOKEN_INIT;
memcpy(args.init.challenge, challenge, size);
arm_smccc_1_2_smc(&args.regs, &args.regs);
if (regs.a0 == RSI_SUCCESS)
return regs.a1;
if (args.regs.a0 == RSI_SUCCESS)
return args.regs.a1;
return -EINVAL;
}