* FAILED: patch "[PATCH] arm64/fpsimd: signal: Forbid non-streaming SVE payload on" failed to apply to 6.6-stable tree
@ 2026-10-05 10:23 gregkh
2026-10-05 22:33 ` [PATCH 6.6.y] arm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: gregkh @ 2026-10-05 10:23 UTC (permalink / raw)
To: mark.rutland, broonie, catalin.marinas, will; +Cc: stable
The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x e060d9069b49fe55f38057dfe592068014652671
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026100535-quiet-manger-898b@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From e060d9069b49fe55f38057dfe592068014652671 Mon Sep 17 00:00:00 2001
From: Mark Rutland <mark.rutland@arm.com>
Date: Thu, 1 Oct 2026 14:08:36 +0100
Subject: [PATCH] arm64/fpsimd: signal: Forbid non-streaming SVE payload on
SME-only systems
When system_supports_sme() is true but system_supports_sve() is false,
restoring a specifically crafted SVE signal context can result in the
task erroneously having non-streaming SVE state. Subsequent attempts to
manipulate the task's FPSIMD/SVE/SME state can result in a variety of
problems, including fatal EL1 UNDEFs.
In such configurations, the kernel always creates an SVE signal context
when delivering a signal, and this can only be in one of two states:
(1) SVE_SIG_FLAG_SM is set, and an SVE payload is present containing
streaming mode SVE state. The recorded VL is the task's live
streaming VL.
(2) SVE_SIG_FLAG_SM is clear, and an SVE payload is not present. The
FPSIMD context contains the non-streaming mode FPSIMD state. The
recorded VL is 0.
Currently restore_sve_fpsimd_context() correctly rejects cases where
SVE_SIG_FLAG_SM is set and an SVE payload is not present, but fails to
reject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is
present. Consequently, restore_sve_fpsimd_context() can place the task
in a state where it has non-streaming SVE state even when this is not
supported by HW.
For example, this can cause a later EL1 UNDEF when the kernel attempts to
restore the task's ZCR_EL1 value:
| # ./sme-sigcontext-to-sve
| Internal error: Oops - Undefined instruction: 0000000002000000 [#1] SMP
| Modules linked in:
| CPU: 0 UID: 0 PID: 131 Comm: sme-sigcontext- Not tainted 7.3.0-rc1 #1 PREEMPT
| Hardware name: linux,dummy-virt (DT)
| pstate: 61402009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
| pc : fpsimd_restore_current_state+0x258/0x458
| lr : exit_to_user_mode_loop+0xb8/0x188
| sp : ffff80008056be40
| x29: ffff80008056be40 x28: fff00000c1670000 x27: 0000000000000000
| x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
| x23: ffff80008056bec0 x22: 0000000000000008 x21: 0000000000000040
| x20: 0000000000000081 x19: 0000000008800010 x18: 0000000000000000
| x17: 0000fffffd412570 x16: 0000000000001000 x15: 0000fffffd4123b0
| x14: 0000fffffd412780 x13: 0000fffffd412be8 x12: 0000000047435300
| x11: 0000fffffd412570 x10: 0000000000000000 x9 : 0000000045585401
| x8 : fff00000c18a6c44 x7 : 0000000000000000 x6 : 0000000000000002
| x5 : 0000000000000002 x4 : ffff800080568000 x3 : 0000000000000001
| x2 : 0000000008800010 x1 : fff00000c1670000 x0 : 0000000008800000
| Call trace:
| fpsimd_restore_current_state+0x258/0x458 (P)
| exit_to_user_mode_loop+0xb8/0x188
| el0_svc+0x1cc/0x1d0
| el0t_64_sync_handler+0xa0/0xe4
| el0t_64_sync+0x198/0x19c
| Code: d5384101 f9400020 53175c03 36b80de0 (d5381202)
| ---[ end trace 0000000000000000 ]---
| Kernel panic - not syncing: Oops - Undefined instruction: Fatal exception in interrupt
| Kernel Offset: 0x291fb1000000 from 0xffff800080000000
| PHYS_OFFSET: 0x40000000
| CPU features: 0x0,00000000,0052802f,ffb88f43,3afcf73f
| Memory Limit: none
Rework restore_sve_fpsimd_context() to reject cases where
SVE_SIG_FLAG_SM is clear and an SVE payload is not present. As
parse_user_sigframe() rejects SVE signal frames when neither SVE nor SME
are supported, it isn't necessary for restore_sve_fpsimd_context() to
handle the case where neither are supported.
Fixes: 7dde62f0687c ("arm64/signal: Always accept SVE signal frames on SME only systems")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 38e6fa204c17..6a06a4e352b1 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -433,6 +433,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
unsigned int vl, vq;
struct user_fpsimd_state fpsimd;
u16 user_vl, flags;
+ bool fpsimd_only;
bool sm;
if (user->sve_size < sizeof(*user->sve))
@@ -443,19 +444,33 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
if (err)
return err;
+ fpsimd_only = (user->sve_size == sizeof(*user->sve));
sm = flags & SVE_SIG_FLAG_SM;
+
if (sm) {
if (!system_supports_sme())
return -EINVAL;
+ /*
+ * Streaming SVE state is always preserved with an SVE payload.
+ * Only accept streaming state which has an SVE payload.
+ */
+ if (fpsimd_only)
+ return -EINVAL;
+
vl = task_get_sme_vl(current);
} else {
/*
- * A SME only system use SVE for streaming mode so can
- * have a SVE formatted context with a zero VL and no
- * payload data.
+ * Non-streaming SVE state may be preserved without an SVE
+ * payload, in which case all state is saved in the FPSIMD
+ * context.
+ *
+ * On SME-only systems, non-streaming (FPSIMD-only) state is
+ * always preserved without an SVE payload, and with VL==0. On
+ * such systems, only accept non-streaming state without an SVE
+ * payload.
*/
- if (!system_supports_sve() && !system_supports_sme())
+ if (!system_supports_sve() && !fpsimd_only)
return -EINVAL;
vl = task_get_sve_vl(current);
@@ -464,16 +479,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
if (user_vl != vl)
return -EINVAL;
- /*
- * Non-streaming SVE state may be preserved without an SVE payload, in
- * which case the SVE context only has a header with VL==0, and all
- * state can be restored from the FPSIMD context.
- *
- * Streaming SVE state is always preserved with an SVE payload. For
- * consistency and robustness, reject restoring streaming SVE state
- * without an SVE payload.
- */
- if (!sm && user->sve_size == sizeof(*user->sve))
+ if (fpsimd_only)
return restore_fpsimd_context(user);
vq = sve_vq_from_vl(vl);
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH 6.6.y] arm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems
2026-10-05 10:23 FAILED: patch "[PATCH] arm64/fpsimd: signal: Forbid non-streaming SVE payload on" failed to apply to 6.6-stable tree gregkh
@ 2026-10-05 22:33 ` Sasha Levin
0 siblings, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2026-10-05 22:33 UTC (permalink / raw)
To: stable; +Cc: Mark Rutland, Mark Brown, Catalin Marinas, Will Deacon,
Sasha Levin
From: Mark Rutland <mark.rutland@arm.com>
[ Upstream commit e060d9069b49fe55f38057dfe592068014652671 ]
When system_supports_sme() is true but system_supports_sve() is false,
restoring a specifically crafted SVE signal context can result in the
task erroneously having non-streaming SVE state. Subsequent attempts to
manipulate the task's FPSIMD/SVE/SME state can result in a variety of
problems, including fatal EL1 UNDEFs.
In such configurations, the kernel always creates an SVE signal context
when delivering a signal, and this can only be in one of two states:
(1) SVE_SIG_FLAG_SM is set, and an SVE payload is present containing
streaming mode SVE state. The recorded VL is the task's live
streaming VL.
(2) SVE_SIG_FLAG_SM is clear, and an SVE payload is not present. The
FPSIMD context contains the non-streaming mode FPSIMD state. The
recorded VL is 0.
Currently restore_sve_fpsimd_context() correctly rejects cases where
SVE_SIG_FLAG_SM is set and an SVE payload is not present, but fails to
reject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is
present. Consequently, restore_sve_fpsimd_context() can place the task
in a state where it has non-streaming SVE state even when this is not
supported by HW.
For example, this can cause a later EL1 UNDEF when the kernel attempts to
restore the task's ZCR_EL1 value:
| # ./sme-sigcontext-to-sve
| Internal error: Oops - Undefined instruction: 0000000002000000 [#1] SMP
| Modules linked in:
| CPU: 0 UID: 0 PID: 131 Comm: sme-sigcontext- Not tainted 7.3.0-rc1 #1 PREEMPT
| Hardware name: linux,dummy-virt (DT)
| pstate: 61402009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
| pc : fpsimd_restore_current_state+0x258/0x458
| lr : exit_to_user_mode_loop+0xb8/0x188
| sp : ffff80008056be40
| x29: ffff80008056be40 x28: fff00000c1670000 x27: 0000000000000000
| x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
| x23: ffff80008056bec0 x22: 0000000000000008 x21: 0000000000000040
| x20: 0000000000000081 x19: 0000000008800010 x18: 0000000000000000
| x17: 0000fffffd412570 x16: 0000000000001000 x15: 0000fffffd4123b0
| x14: 0000fffffd412780 x13: 0000fffffd412be8 x12: 0000000047435300
| x11: 0000fffffd412570 x10: 0000000000000000 x9 : 0000000045585401
| x8 : fff00000c18a6c44 x7 : 0000000000000000 x6 : 0000000000000002
| x5 : 0000000000000002 x4 : ffff800080568000 x3 : 0000000000000001
| x2 : 0000000008800010 x1 : fff00000c1670000 x0 : 0000000008800000
| Call trace:
| fpsimd_restore_current_state+0x258/0x458 (P)
| exit_to_user_mode_loop+0xb8/0x188
| el0_svc+0x1cc/0x1d0
| el0t_64_sync_handler+0xa0/0xe4
| el0t_64_sync+0x198/0x19c
| Code: d5384101 f9400020 53175c03 36b80de0 (d5381202)
| ---[ end trace 0000000000000000 ]---
| Kernel panic - not syncing: Oops - Undefined instruction: Fatal exception in interrupt
| Kernel Offset: 0x291fb1000000 from 0xffff800080000000
| PHYS_OFFSET: 0x40000000
| CPU features: 0x0,00000000,0052802f,ffb88f43,3afcf73f
| Memory Limit: none
Rework restore_sve_fpsimd_context() to reject cases where
SVE_SIG_FLAG_SM is clear and an SVE payload is not present. As
parse_user_sigframe() rejects SVE signal frames when neither SVE nor SME
are supported, it isn't necessary for restore_sve_fpsimd_context() to
handle the case where neither are supported.
Fixes: 7dde62f0687c ("arm64/signal: Always accept SVE signal frames on SME only systems")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/kernel/signal.c | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 032afb40dfa77..506d4b9f725c1 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -286,6 +286,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
unsigned int vl, vq;
struct user_fpsimd_state fpsimd;
u16 user_vl, flags;
+ bool fpsimd_only;
bool sm;
if (user->sve_size < sizeof(*user->sve))
@@ -296,19 +297,33 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
if (err)
return err;
+ fpsimd_only = (user->sve_size == sizeof(*user->sve));
sm = flags & SVE_SIG_FLAG_SM;
+
if (sm) {
if (!system_supports_sme())
return -EINVAL;
+ /*
+ * Streaming SVE state is always preserved with an SVE payload.
+ * Only accept streaming state which has an SVE payload.
+ */
+ if (fpsimd_only)
+ return -EINVAL;
+
vl = task_get_sme_vl(current);
} else {
/*
- * A SME only system use SVE for streaming mode so can
- * have a SVE formatted context with a zero VL and no
- * payload data.
+ * Non-streaming SVE state may be preserved without an SVE
+ * payload, in which case all state is saved in the FPSIMD
+ * context.
+ *
+ * On SME-only systems, non-streaming (FPSIMD-only) state is
+ * always preserved without an SVE payload, and with VL==0. On
+ * such systems, only accept non-streaming state without an SVE
+ * payload.
*/
- if (!system_supports_sve() && !system_supports_sme())
+ if (!system_supports_sve() && !fpsimd_only)
return -EINVAL;
vl = task_get_sve_vl(current);
@@ -317,16 +332,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
if (user_vl != vl)
return -EINVAL;
- /*
- * Non-streaming SVE state may be preserved without an SVE payload, in
- * which case the SVE context only has a header with VL==0, and all
- * state can be restored from the FPSIMD context.
- *
- * Streaming SVE state is always preserved with an SVE payload. For
- * consistency and robustness, reject restoring streaming SVE state
- * without an SVE payload.
- */
- if (!sm && user->sve_size == sizeof(*user->sve))
+ if (fpsimd_only)
return restore_fpsimd_context(user);
vq = sve_vq_from_vl(vl);
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2026-10-05 10:23 FAILED: patch "[PATCH] arm64/fpsimd: signal: Forbid non-streaming SVE payload on" failed to apply to 6.6-stable tree gregkh
2026-10-05 22:33 ` [PATCH 6.6.y] arm64/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems Sasha Levin
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