From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: barebox@lists.infradead.org
Cc: lst@pengutronix.de, Ahmad Fatoum <a.fatoum@pengutronix.de>
Subject: [PATCH 2/4] KASan: implement non-warning kasan_is_poisoned_shadow
Date: Tue, 10 Sep 2024 13:48:30 +0200 [thread overview]
Message-ID: <20240910114832.2984195-3-a.fatoum@pengutronix.de> (raw)
In-Reply-To: <20240910114832.2984195-1-a.fatoum@pengutronix.de>
We export kasan_poison_shadow and kasan_unpoison_shadow for use by
allocators, but provide no API to query whether a region is poisoned
without triggering a stack trace.
This can be useful however for more unconventional "allocators" like the
DMA API debug code, which can use it to detect double poisons/unpoisons
that should not occur if the DMA API is correctly used.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
include/linux/kasan.h | 2 ++
lib/kasan/generic.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 39 insertions(+)
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 5fa0bebb796b..7812e0fa805b 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -69,6 +69,7 @@ extern void kasan_disable_current(void);
void kasan_poison_shadow(const void *address, size_t size, u8 value);
void kasan_unpoison_shadow(const void *address, size_t size);
+int kasan_is_poisoned_shadow(const void *address, size_t size);
bool kasan_save_enable_multi_shot(void);
void kasan_restore_multi_shot(bool enabled);
@@ -77,6 +78,7 @@ void kasan_restore_multi_shot(bool enabled);
static inline void kasan_poison_shadow(const void *address, size_t size, u8 value) {}
static inline void kasan_unpoison_shadow(const void *address, size_t size) {}
+static inline int kasan_is_poisoned_shadow(const void *address, size_t size) { return -1; }
static inline void kasan_enable_current(void) {}
static inline void kasan_disable_current(void) {}
diff --git a/lib/kasan/generic.c b/lib/kasan/generic.c
index 3709b8da9aae..2432f9274401 100644
--- a/lib/kasan/generic.c
+++ b/lib/kasan/generic.c
@@ -177,6 +177,43 @@ static __always_inline bool check_memory_region_inline(unsigned long addr,
return !kasan_report(addr, size, write, ret_ip);
}
+int kasan_is_poisoned_shadow(const void *_addr, size_t size)
+{
+ unsigned long addr = (unsigned long)_addr;
+ unsigned long ret;
+
+ if (!kasan_initialized)
+ return -1;
+
+ if (addr < kasan_shadow_start)
+ return -1;
+
+ if (addr > kasan_shadowed_end)
+ return -1;
+
+ if (unlikely(size == 0))
+ return -1;
+
+ if (unlikely(addr + size < addr))
+ return -1;
+
+ if (addr < kasan_shadow_base)
+ return -1;
+
+ ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr),
+ kasan_mem_to_shadow((void *)addr + size - 1) + 1);
+
+ if (unlikely(ret)) {
+ unsigned long last_byte = addr + size - 1;
+ s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
+
+ if (unlikely(ret != (unsigned long)last_shadow ||
+ ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
+ return 1;
+ }
+ return 0;
+}
+
void kasan_init(unsigned long membase, unsigned long memsize,
unsigned long shadow_base)
{
--
2.39.2
next prev parent reply other threads:[~2024-09-10 11:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-10 11:48 [PATCH 0/4] dma: debug: track DMA buffer ownership with KASAN Ahmad Fatoum
2024-09-10 11:48 ` [PATCH 1/4] Revert "dma: debug: detect repeated DMA sync" Ahmad Fatoum
2024-09-10 11:48 ` Ahmad Fatoum [this message]
2024-09-10 11:48 ` [PATCH 3/4] dma: debug: poison DMA buffers with KASAN while owned by device Ahmad Fatoum
2024-09-10 11:48 ` [PATCH 4/4] dma: debug: detect repeated DMA sync using KASAN Ahmad Fatoum
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