kstack_offset was previously maintained per-cpu, but this caused a
couple of issues. So let's instead make it per-task.
Issue 1: add_random_kstack_offset() and choose_random_kstack_offset()
expected and required to be called with interrupts and preemption
disabled so that it could manipulate per-cpu state. But arm64, loongarch
and risc-v are calling them with interrupts and preemption enabled. I
don't _think_ this causes any functional issues, but it's certainly
unexpected and could lead to manipulating the wrong cpu's state, which
could cause a minor performance degradation due to bouncing the cache
lines. By maintaining the state per-task those functions can safely be
called in preemptible context.
Issue 2: add_random_kstack_offset() is called before executing the
syscall and expands the stack using a previously chosen rnadom offset.
choose_random_kstack_offset() is called after executing the syscall and
chooses and stores a new random offset for the next syscall. With
per-cpu storage for this offset, an attacker could force cpu migration
during the execution of the syscall and prevent the offset from being
updated for the original cpu such that it is predictable for the next
syscall on that cpu. By maintaining the state per-task, this problem
goes away because the per-task random offset is updated after the
syscall regardless of which cpu it is executing on.
Fixes: 39218ff4c625 ("stack: Optionally randomize kernel stack offset each syscall")
Closes: https://lore.kernel.org/all/dd8c37bc-795f-4c7a-9086-69e584d8ab24@arm.com/
Cc: stable(a)vger.kernel.org
Signed-off-by: Ryan Roberts <ryan.roberts(a)arm.com>
---
include/linux/randomize_kstack.h | 26 +++++++++++++++-----------
include/linux/sched.h | 4 ++++
init/main.c | 1 -
kernel/fork.c | 2 ++
4 files changed, 21 insertions(+), 12 deletions(-)
diff --git a/include/linux/randomize_kstack.h b/include/linux/randomize_kstack.h
index 1d982dbdd0d0..089b1432f7e6 100644
--- a/include/linux/randomize_kstack.h
+++ b/include/linux/randomize_kstack.h
@@ -9,7 +9,6 @@
DECLARE_STATIC_KEY_MAYBE(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT,
randomize_kstack_offset);
-DECLARE_PER_CPU(u32, kstack_offset);
/*
* Do not use this anywhere else in the kernel. This is used here because
@@ -50,15 +49,14 @@ DECLARE_PER_CPU(u32, kstack_offset);
* add_random_kstack_offset - Increase stack utilization by previously
* chosen random offset
*
- * This should be used in the syscall entry path when interrupts and
- * preempt are disabled, and after user registers have been stored to
- * the stack. For testing the resulting entropy, please see:
- * tools/testing/selftests/lkdtm/stack-entropy.sh
+ * This should be used in the syscall entry path after user registers have been
+ * stored to the stack. Preemption may be enabled. For testing the resulting
+ * entropy, please see: tools/testing/selftests/lkdtm/stack-entropy.sh
*/
#define add_random_kstack_offset() do { \
if (static_branch_maybe(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT, \
&randomize_kstack_offset)) { \
- u32 offset = raw_cpu_read(kstack_offset); \
+ u32 offset = current->kstack_offset; \
u8 *ptr = __kstack_alloca(KSTACK_OFFSET_MAX(offset)); \
/* Keep allocation even after "ptr" loses scope. */ \
asm volatile("" :: "r"(ptr) : "memory"); \
@@ -69,9 +67,9 @@ DECLARE_PER_CPU(u32, kstack_offset);
* choose_random_kstack_offset - Choose the random offset for the next
* add_random_kstack_offset()
*
- * This should only be used during syscall exit when interrupts and
- * preempt are disabled. This position in the syscall flow is done to
- * frustrate attacks from userspace attempting to learn the next offset:
+ * This should only be used during syscall exit. Preemption may be enabled. This
+ * position in the syscall flow is done to frustrate attacks from userspace
+ * attempting to learn the next offset:
* - Maximize the timing uncertainty visible from userspace: if the
* offset is chosen at syscall entry, userspace has much more control
* over the timing between choosing offsets. "How long will we be in
@@ -85,14 +83,20 @@ DECLARE_PER_CPU(u32, kstack_offset);
#define choose_random_kstack_offset(rand) do { \
if (static_branch_maybe(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT, \
&randomize_kstack_offset)) { \
- u32 offset = raw_cpu_read(kstack_offset); \
+ u32 offset = current->kstack_offset; \
offset = ror32(offset, 5) ^ (rand); \
- raw_cpu_write(kstack_offset, offset); \
+ current->kstack_offset = offset; \
} \
} while (0)
+
+static inline void random_kstack_task_init(struct task_struct *tsk)
+{
+ current->kstack_offset = 0;
+}
#else /* CONFIG_RANDOMIZE_KSTACK_OFFSET */
#define add_random_kstack_offset() do { } while (0)
#define choose_random_kstack_offset(rand) do { } while (0)
+#define random_kstack_task_init(tsk) do { } while (0)
#endif /* CONFIG_RANDOMIZE_KSTACK_OFFSET */
#endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b469878de25c..dae227d217ef 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1613,6 +1613,10 @@ struct task_struct {
unsigned long prev_lowest_stack;
#endif
+#ifdef CONFIG_RANDOMIZE_KSTACK_OFFSET
+ u32 kstack_offset;
+#endif
+
#ifdef CONFIG_X86_MCE
void __user *mce_vaddr;
__u64 mce_kflags;
diff --git a/init/main.c b/init/main.c
index 07a3116811c5..048a62538242 100644
--- a/init/main.c
+++ b/init/main.c
@@ -830,7 +830,6 @@ static inline void initcall_debug_enable(void)
#ifdef CONFIG_RANDOMIZE_KSTACK_OFFSET
DEFINE_STATIC_KEY_MAYBE_RO(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT,
randomize_kstack_offset);
-DEFINE_PER_CPU(u32, kstack_offset);
static int __init early_randomize_kstack_offset(char *buf)
{
diff --git a/kernel/fork.c b/kernel/fork.c
index 3da0f08615a9..c0dced542b8a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -95,6 +95,7 @@
#include <linux/thread_info.h>
#include <linux/kstack_erase.h>
#include <linux/kasan.h>
+#include <linux/randomize_kstack.h>
#include <linux/scs.h>
#include <linux/io_uring.h>
#include <linux/bpf.h>
@@ -2191,6 +2192,7 @@ __latent_entropy struct task_struct *copy_process(
if (retval)
goto bad_fork_cleanup_io;
+ random_kstack_task_init(p);
stackleak_task_init(p);
if (pid != &init_struct_pid) {
--
2.43.0
Set CLK_IGNORE_UNUSED flag to clock adsp audio26m to prevent disabling
this clock during early boot, as turning it off causes other modules
to fail probing and leads to boot failures in ARM SystemReady test cases
and the EFI boot process (on Linux Distributions, for example, debian,
openSuse, etc.). Without this flag, disabling unused clocks cannot
complete properly after adsp_audio26m is turned off.
Fixes: 0d2f2cefba64 ("clk: mediatek: Add MT8188 adsp clock support")
Cc: Stable(a)vger.kernel.org
Signed-off-by: Macpaul Lin <macpaul.lin(a)mediatek.com>
---
drivers/clk/mediatek/clk-mt8188-adsp_audio26m.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/clk/mediatek/clk-mt8188-adsp_audio26m.c b/drivers/clk/mediatek/clk-mt8188-adsp_audio26m.c
index dcde2187d24a..b9fe66ef4f2e 100644
--- a/drivers/clk/mediatek/clk-mt8188-adsp_audio26m.c
+++ b/drivers/clk/mediatek/clk-mt8188-adsp_audio26m.c
@@ -20,8 +20,8 @@ static const struct mtk_gate_regs adsp_audio26m_cg_regs = {
};
#define GATE_ADSP_FLAGS(_id, _name, _parent, _shift) \
- GATE_MTK(_id, _name, _parent, &adsp_audio26m_cg_regs, _shift, \
- &mtk_clk_gate_ops_no_setclr)
+ GATE_MTK_FLAGS(_id, _name, _parent, &adsp_audio26m_cg_regs, _shift, \
+ &mtk_clk_gate_ops_no_setclr, CLK_IGNORE_UNUSED)
static const struct mtk_gate adsp_audio26m_clks[] = {
GATE_ADSP_FLAGS(CLK_AUDIODSP_AUDIO26M, "audiodsp_audio26m", "clk26m", 3),
--
2.45.2
Dzień dobry,
pomagamy przedsiębiorcom wprowadzić model wymiany walut, który minimalizuje wahania kosztów przy rozliczeniach międzynarodowych.
Kiedyv możemy umówić się na 15-minutową rozmowę, aby zaprezentować, jak taki model mógłby działać w Państwa firmie - z gwarancją indywidualnych kursów i pełnym uproszczeniem płatności? Proszę o propozycję dogodnego terminu.
Pozdrawiam
Marek Poradecki
Building htmldocs generates a warning:
WARNING: include/uapi/linux/media/amlogic/c3-isp-config.h:199
error: Cannot parse struct or union!
Which correctly highlights that the c3_isp_params_block_header symbol
is wrongly documented as a struct while it's a plain #define instead.
Fix this by removing the 'struct' identifier from the documentation of
the c3_isp_params_block_header symbol.
Reported-by: Stephen Rothwell <sfr(a)canb.auug.org.au>
Fixes: 45662082855c ("media: uapi: Convert Amlogic C3 to V4L2 extensible params")
Cc: stable(a)vger.kernel.org
Signed-off-by: Jacopo Mondi <jacopo.mondi(a)ideasonboard.com>
---
Stephen reported this error on linux-next. Please collect this patch for v6.19.
I'm not sure this qualifies for stable, as it will ideally land in the same
release as the patch that introduces the warning. If that's not the case, please
strip:
Fixes: 45662082855c ("media: uapi: Convert Amlogic C3 to V4L2 extensible params")
Cc: stable(a)vger.kernel.org
from the commit message when applying, thanks!
---
include/uapi/linux/media/amlogic/c3-isp-config.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/uapi/linux/media/amlogic/c3-isp-config.h b/include/uapi/linux/media/amlogic/c3-isp-config.h
index 0a3c1cc55ccb..92db5dcdda18 100644
--- a/include/uapi/linux/media/amlogic/c3-isp-config.h
+++ b/include/uapi/linux/media/amlogic/c3-isp-config.h
@@ -186,7 +186,7 @@ enum c3_isp_params_block_type {
#define C3_ISP_PARAMS_BLOCK_FL_ENABLE V4L2_ISP_PARAMS_FL_BLOCK_ENABLE
/**
- * struct c3_isp_params_block_header - C3 ISP parameter block header
+ * c3_isp_params_block_header - C3 ISP parameter block header
*
* This structure represents the common part of all the ISP configuration
* blocks and is identical to :c:type:`v4l2_isp_params_block_header`.
--
2.51.1