* [PATCH kcsan 1/2] instrumented.h: Fix all kernel-doc format warnings
2023-03-21 0:59 [PATCH kcsan 0/2] KCSAN updates for v6.4 Paul E. McKenney
@ 2023-03-21 0:59 ` Paul E. McKenney
2023-03-21 0:59 ` [PATCH kcsan 2/2] kcsan: Avoid READ_ONCE() in read_instrumented_memory() Paul E. McKenney
1 sibling, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2023-03-21 0:59 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng,
Randy Dunlap, Arnd Bergmann, Andrew Morton, Paul E . McKenney
From: Randy Dunlap <rdunlap@infradead.org>
Fix 26 kernel-doc notation warnings by converting the function
documentation to kernel-doc format.
Warning example:
instrumented.h:155: warning: Function parameter or member 'to' not described in 'instrument_copy_from_user_after'
instrumented.h:155: warning: Function parameter or member 'from' not described in 'instrument_copy_from_user_after'
instrumented.h:155: warning: Function parameter or member 'n' not described in 'instrument_copy_from_user_after'
instrumented.h:155: warning: Function parameter or member 'left' not described in 'instrument_copy_from_user_after'
Fixes: 36e4d4dd4fc4 ("include/linux: Add instrumented.h infrastructure")
Fixes: 00047c2e6d7c ("instrumented.h: Introduce read-write instrumentation hooks")
Fixes: 33b75c1d884e ("instrumented.h: allow instrumenting both sides of copy_from_user()")
Fixes: 888f84a6da4d ("x86: asm: instrument usercopy in get_user() and put_user()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/instrumented.h | 63 +++++++++++++++---------------------
1 file changed, 26 insertions(+), 37 deletions(-)
diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
index 501fa8486749..1b608e00290a 100644
--- a/include/linux/instrumented.h
+++ b/include/linux/instrumented.h
@@ -15,12 +15,11 @@
/**
* instrument_read - instrument regular read access
+ * @v: address of access
+ * @size: size of access
*
* Instrument a regular read access. The instrumentation should be inserted
* before the actual read happens.
- *
- * @ptr address of access
- * @size size of access
*/
static __always_inline void instrument_read(const volatile void *v, size_t size)
{
@@ -30,12 +29,11 @@ static __always_inline void instrument_read(const volatile void *v, size_t size)
/**
* instrument_write - instrument regular write access
+ * @v: address of access
+ * @size: size of access
*
* Instrument a regular write access. The instrumentation should be inserted
* before the actual write happens.
- *
- * @ptr address of access
- * @size size of access
*/
static __always_inline void instrument_write(const volatile void *v, size_t size)
{
@@ -45,12 +43,11 @@ static __always_inline void instrument_write(const volatile void *v, size_t size
/**
* instrument_read_write - instrument regular read-write access
+ * @v: address of access
+ * @size: size of access
*
* Instrument a regular write access. The instrumentation should be inserted
* before the actual write happens.
- *
- * @ptr address of access
- * @size size of access
*/
static __always_inline void instrument_read_write(const volatile void *v, size_t size)
{
@@ -60,12 +57,11 @@ static __always_inline void instrument_read_write(const volatile void *v, size_t
/**
* instrument_atomic_read - instrument atomic read access
+ * @v: address of access
+ * @size: size of access
*
* Instrument an atomic read access. The instrumentation should be inserted
* before the actual read happens.
- *
- * @ptr address of access
- * @size size of access
*/
static __always_inline void instrument_atomic_read(const volatile void *v, size_t size)
{
@@ -75,12 +71,11 @@ static __always_inline void instrument_atomic_read(const volatile void *v, size_
/**
* instrument_atomic_write - instrument atomic write access
+ * @v: address of access
+ * @size: size of access
*
* Instrument an atomic write access. The instrumentation should be inserted
* before the actual write happens.
- *
- * @ptr address of access
- * @size size of access
*/
static __always_inline void instrument_atomic_write(const volatile void *v, size_t size)
{
@@ -90,12 +85,11 @@ static __always_inline void instrument_atomic_write(const volatile void *v, size
/**
* instrument_atomic_read_write - instrument atomic read-write access
+ * @v: address of access
+ * @size: size of access
*
* Instrument an atomic read-write access. The instrumentation should be
* inserted before the actual write happens.
- *
- * @ptr address of access
- * @size size of access
*/
static __always_inline void instrument_atomic_read_write(const volatile void *v, size_t size)
{
@@ -105,13 +99,12 @@ static __always_inline void instrument_atomic_read_write(const volatile void *v,
/**
* instrument_copy_to_user - instrument reads of copy_to_user
+ * @to: destination address
+ * @from: source address
+ * @n: number of bytes to copy
*
* Instrument reads from kernel memory, that are due to copy_to_user (and
* variants). The instrumentation must be inserted before the accesses.
- *
- * @to destination address
- * @from source address
- * @n number of bytes to copy
*/
static __always_inline void
instrument_copy_to_user(void __user *to, const void *from, unsigned long n)
@@ -123,13 +116,12 @@ instrument_copy_to_user(void __user *to, const void *from, unsigned long n)
/**
* instrument_copy_from_user_before - add instrumentation before copy_from_user
+ * @to: destination address
+ * @from: source address
+ * @n: number of bytes to copy
*
* Instrument writes to kernel memory, that are due to copy_from_user (and
* variants). The instrumentation should be inserted before the accesses.
- *
- * @to destination address
- * @from source address
- * @n number of bytes to copy
*/
static __always_inline void
instrument_copy_from_user_before(const void *to, const void __user *from, unsigned long n)
@@ -140,14 +132,13 @@ instrument_copy_from_user_before(const void *to, const void __user *from, unsign
/**
* instrument_copy_from_user_after - add instrumentation after copy_from_user
+ * @to: destination address
+ * @from: source address
+ * @n: number of bytes to copy
+ * @left: number of bytes not copied (as returned by copy_from_user)
*
* Instrument writes to kernel memory, that are due to copy_from_user (and
* variants). The instrumentation should be inserted after the accesses.
- *
- * @to destination address
- * @from source address
- * @n number of bytes to copy
- * @left number of bytes not copied (as returned by copy_from_user)
*/
static __always_inline void
instrument_copy_from_user_after(const void *to, const void __user *from,
@@ -158,12 +149,11 @@ instrument_copy_from_user_after(const void *to, const void __user *from,
/**
* instrument_get_user() - add instrumentation to get_user()-like macros
+ * @to: destination variable, may not be address-taken
*
* get_user() and friends are fragile, so it may depend on the implementation
* whether the instrumentation happens before or after the data is copied from
* the userspace.
- *
- * @to destination variable, may not be address-taken
*/
#define instrument_get_user(to) \
({ \
@@ -175,14 +165,13 @@ instrument_copy_from_user_after(const void *to, const void __user *from,
/**
* instrument_put_user() - add instrumentation to put_user()-like macros
+ * @from: source address
+ * @ptr: userspace pointer to copy to
+ * @size: number of bytes to copy
*
* put_user() and friends are fragile, so it may depend on the implementation
* whether the instrumentation happens before or after the data is copied from
* the userspace.
- *
- * @from source address
- * @ptr userspace pointer to copy to
- * @size number of bytes to copy
*/
#define instrument_put_user(from, ptr, size) \
({ \
--
2.40.0.rc2
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH kcsan 2/2] kcsan: Avoid READ_ONCE() in read_instrumented_memory()
2023-03-21 0:59 [PATCH kcsan 0/2] KCSAN updates for v6.4 Paul E. McKenney
2023-03-21 0:59 ` [PATCH kcsan 1/2] instrumented.h: Fix all kernel-doc format warnings Paul E. McKenney
@ 2023-03-21 0:59 ` Paul E. McKenney
1 sibling, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2023-03-21 0:59 UTC (permalink / raw)
To: linux-kernel, kasan-dev, kernel-team, mingo
Cc: elver, andreyknvl, glider, dvyukov, cai, boqun.feng, Haibo Li,
stable, Paul E . McKenney
From: Marco Elver <elver@google.com>
Haibo Li reported:
| Unable to handle kernel paging request at virtual address
| ffffff802a0d8d7171
| Mem abort info:o:
| ESR = 0x9600002121
| EC = 0x25: DABT (current EL), IL = 32 bitsts
| SET = 0, FnV = 0 0
| EA = 0, S1PTW = 0 0
| FSC = 0x21: alignment fault
| Data abort info:o:
| ISV = 0, ISS = 0x0000002121
| CM = 0, WnR = 0 0
| swapper pgtable: 4k pages, 39-bit VAs, pgdp=000000002835200000
| [ffffff802a0d8d71] pgd=180000005fbf9003, p4d=180000005fbf9003,
| pud=180000005fbf9003, pmd=180000005fbe8003, pte=006800002a0d8707
| Internal error: Oops: 96000021 [#1] PREEMPT SMP
| Modules linked in:
| CPU: 2 PID: 45 Comm: kworker/u8:2 Not tainted
| 5.15.78-android13-8-g63561175bbda-dirty #1
| ...
| pc : kcsan_setup_watchpoint+0x26c/0x6bc
| lr : kcsan_setup_watchpoint+0x88/0x6bc
| sp : ffffffc00ab4b7f0
| x29: ffffffc00ab4b800 x28: ffffff80294fe588 x27: 0000000000000001
| x26: 0000000000000019 x25: 0000000000000001 x24: ffffff80294fdb80
| x23: 0000000000000000 x22: ffffffc00a70fb68 x21: ffffff802a0d8d71
| x20: 0000000000000002 x19: 0000000000000000 x18: ffffffc00a9bd060
| x17: 0000000000000001 x16: 0000000000000000 x15: ffffffc00a59f000
| x14: 0000000000000001 x13: 0000000000000000 x12: ffffffc00a70faa0
| x11: 00000000aaaaaaab x10: 0000000000000054 x9 : ffffffc00839adf8
| x8 : ffffffc009b4cf00 x7 : 0000000000000000 x6 : 0000000000000007
| x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffffffc00a70fb70
| x2 : 0005ff802a0d8d71 x1 : 0000000000000000 x0 : 0000000000000000
| Call trace:
| kcsan_setup_watchpoint+0x26c/0x6bc
| __tsan_read2+0x1f0/0x234
| inflate_fast+0x498/0x750
| zlib_inflate+0x1304/0x2384
| __gunzip+0x3a0/0x45c
| gunzip+0x20/0x30
| unpack_to_rootfs+0x2a8/0x3fc
| do_populate_rootfs+0xe8/0x11c
| async_run_entry_fn+0x58/0x1bc
| process_one_work+0x3ec/0x738
| worker_thread+0x4c4/0x838
| kthread+0x20c/0x258
| ret_from_fork+0x10/0x20
| Code: b8bfc2a8 2a0803f7 14000007 d503249f (78bfc2a8) )
| ---[ end trace 613a943cb0a572b6 ]-----
The reason for this is that on certain arm64 configuration since
e35123d83ee3 ("arm64: lto: Strengthen READ_ONCE() to acquire when
CONFIG_LTO=y"), READ_ONCE() may be promoted to a full atomic acquire
instruction which cannot be used on unaligned addresses.
Fix it by avoiding READ_ONCE() in read_instrumented_memory(), and simply
forcing the compiler to do the required access by casting to the
appropriate volatile type. In terms of generated code this currently
only affects architectures that do not use the default READ_ONCE()
implementation.
The only downside is that we are not guaranteed atomicity of the access
itself, although on most architectures a plain load up to machine word
size should still be atomic (a fact the default READ_ONCE() still relies
on itself).
Reported-by: Haibo Li <haibo.li@mediatek.com>
Tested-by: Haibo Li <haibo.li@mediatek.com>
Cc: <stable@vger.kernel.org> # 5.17+
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/kcsan/core.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 54d077e1a2dc..5a60cc52adc0 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -337,11 +337,20 @@ static void delay_access(int type)
*/
static __always_inline u64 read_instrumented_memory(const volatile void *ptr, size_t size)
{
+ /*
+ * In the below we don't necessarily need the read of the location to
+ * be atomic, and we don't use READ_ONCE(), since all we need for race
+ * detection is to observe 2 different values.
+ *
+ * Furthermore, on certain architectures (such as arm64), READ_ONCE()
+ * may turn into more complex instructions than a plain load that cannot
+ * do unaligned accesses.
+ */
switch (size) {
- case 1: return READ_ONCE(*(const u8 *)ptr);
- case 2: return READ_ONCE(*(const u16 *)ptr);
- case 4: return READ_ONCE(*(const u32 *)ptr);
- case 8: return READ_ONCE(*(const u64 *)ptr);
+ case 1: return *(const volatile u8 *)ptr;
+ case 2: return *(const volatile u16 *)ptr;
+ case 4: return *(const volatile u32 *)ptr;
+ case 8: return *(const volatile u64 *)ptr;
default: return 0; /* Ignore; we do not diff the values. */
}
}
--
2.40.0.rc2
^ permalink raw reply [flat|nested] 3+ messages in thread