linux-kernel - [PATCH v2 2/6] arm64/signal: Remove redundant size validation from parse_user

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Message-Id: <20221212-arm64-signal-cleanup-v2-2-14a8f3e088b7@kernel.org>
Date:   Tue, 03 Jan 2023 20:25:16 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH v2 2/6] arm64/signal: Remove redundant size validation from
 parse_user_sigframe()

There is some minimal size validation in parse_user_sigframe() however
all of the individual parsing functions perform frame specific validation
of the sizing information, remove the frame specific size checks in the
core so that there isn't any confusion about what we validate for size.

Since the checks in the SVE and ZA parsing are after we have read the
relevant context and since they won't report an error if the frame is
undersized they are adjusted to check for this before doing anything else.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/kernel/signal.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 9d3d10269da7..a7b4bb584d17 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -274,6 +274,9 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
 	if (__copy_from_user(&sve, user->sve, sizeof(sve)))
 		return -EFAULT;
 
+	if (sve.head.size < sizeof(*user->sve))
+		return -EINVAL;
+
 	if (sve.flags & SVE_SIG_FLAG_SM) {
 		if (!system_supports_sme())
 			return -EINVAL;
@@ -289,7 +292,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
 	if (sve.vl != vl)
 		return -EINVAL;
 
-	if (sve.head.size <= sizeof(*user->sve)) {
+	if (sve.head.size == sizeof(*user->sve)) {
 		clear_thread_flag(TIF_SVE);
 		current->thread.svcr &= ~SVCR_SM_MASK;
 		current->thread.fp_type = FP_STATE_FPSIMD;
@@ -404,10 +407,13 @@ static int restore_za_context(struct user_ctxs *user)
 	if (__copy_from_user(&za, user->za, sizeof(za)))
 		return -EFAULT;
 
+	if (za.head.size < sizeof(*user->za))
+		return -EINVAL;
+
 	if (za.vl != task_get_sme_vl(current))
 		return -EINVAL;
 
-	if (za.head.size <= sizeof(*user->za)) {
+	if (za.head.size == sizeof(*user->za)) {
 		current->thread.svcr &= ~SVCR_ZA_MASK;
 		return 0;
 	}
@@ -510,9 +516,6 @@ static int parse_user_sigframe(struct user_ctxs *user,
 			if (user->fpsimd)
 				goto invalid;
 
-			if (size < sizeof(*user->fpsimd))
-				goto invalid;
-
 			user->fpsimd = (struct fpsimd_context __user *)head;
 			break;
 
@@ -527,9 +530,6 @@ static int parse_user_sigframe(struct user_ctxs *user,
 			if (user->sve)
 				goto invalid;
 
-			if (size < sizeof(*user->sve))
-				goto invalid;
-
 			user->sve = (struct sve_context __user *)head;
 			break;
 
@@ -540,9 +540,6 @@ static int parse_user_sigframe(struct user_ctxs *user,
 			if (user->za)
 				goto invalid;
 
-			if (size < sizeof(*user->za))
-				goto invalid;
-
 			user->za = (struct za_context __user *)head;
 			break;
 

-- 
2.30.2