[PATCH v1 2/6] arm64/signal: Remove redundant size validation from parse_user_sigframe()

[Mark Brown]

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 at kernel.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 f9a98948a2c8..1840e26f3f54 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -270,6 +270,9 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
 	struct user_fpsimd_state fpsimd;
 	struct sve_context sve;
 
+	if (sve.head.size < sizeof(*user->sve))
+		return -EINVAL;
+
 	if (__copy_from_user(&sve, user->sve, sizeof(sve)))
 		return -EFAULT;
 
@@ -288,7 +291,7 @@ 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;
 		goto fpsimd_only;
@@ -398,13 +401,16 @@ static int restore_za_context(struct user_ctxs *user)
 	unsigned int vq;
 	struct za_context za;
 
+	if (za.head.size == sizeof(*user->za))
+		return -EINVAL;
+
 	if (__copy_from_user(&za, user->za, sizeof(za)))
 		return -EFAULT;
 
 	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;
 	}
@@ -507,9 +513,6 @@ 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;
 
@@ -524,9 +527,6 @@ 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;
 
@@ -537,9 +537,6 @@ 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