[PATCH v7 20/38] lib/zlib: Unpoison DFLTCC output buffers

Ilya Leoshkevich
2024-06-21T11:37:47Z

The constraints of the DFLTCC inline assembly are not precise: they
do not communicate the size of the output buffers to the compiler, so
it cannot automatically instrument it.

Add the manual kmsan_unpoison_memory() calls for the output buffers.
The logic is the same as in [1].

[1] https://github.com/zlib-ng/zlib-ng/commit/1f5ddcc009ac3511e99fc88736a9e1a6381168c5

Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
lib/zlib_dfltcc/dfltcc.h | 1 +
lib/zlib_dfltcc/dfltcc_util.h | 28 ++++++++++++++++++++++++++++
2 files changed, 29 insertions(+)

diff --git a/lib/zlib_dfltcc/dfltcc.h b/lib/zlib_dfltcc/dfltcc.h
index b96232bdd44d..0f2a16d7a48a 100644
--- a/lib/zlib_dfltcc/dfltcc.h
+++ b/lib/zlib_dfltcc/dfltcc.h
@@ -80,6 +80,7 @@ struct dfltcc_param_v0 {
uint8_t csb[1152];
};

+static_assert(offsetof(struct dfltcc_param_v0, csb) == 384);
static_assert(sizeof(struct dfltcc_param_v0) == 1536);

#define CVT_CRC32 0
diff --git a/lib/zlib_dfltcc/dfltcc_util.h b/lib/zlib_dfltcc/dfltcc_util.h
index 4a46b5009f0d..10509270d822 100644
--- a/lib/zlib_dfltcc/dfltcc_util.h
+++ b/lib/zlib_dfltcc/dfltcc_util.h
@@ -2,6 +2,8 @@
#ifndef DFLTCC_UTIL_H
#define DFLTCC_UTIL_H

+#include "dfltcc.h"
+#include <linux/kmsan-checks.h>
#include <linux/zutil.h>

/*
@@ -20,6 +22,7 @@ typedef enum {
#define DFLTCC_CMPR 2
#define DFLTCC_XPND 4
#define HBT_CIRCULAR (1 << 7)
+#define DFLTCC_FN_MASK ((1 << 7) - 1)
#define HB_BITS 15
#define HB_SIZE (1 << HB_BITS)

@@ -34,6 +37,7 @@ static inline dfltcc_cc dfltcc(
)
{
Byte *t2 = op1 ? *op1 : NULL;
+ unsigned char *orig_t2 = t2;
size_t t3 = len1 ? *len1 : 0;
const Byte *t4 = op2 ? *op2 : NULL;
size_t t5 = len2 ? *len2 : 0;
@@ -59,6 +63,30 @@ static inline dfltcc_cc dfltcc(
: "cc", "memory");
t2 = r2; t3 = r3; t4 = r4; t5 = r5;

+ /*
+ * Unpoison the parameter block and the output buffer.
+ * This is a no-op in non-KMSAN builds.
+ */
+ switch (fn & DFLTCC_FN_MASK) {
+ case DFLTCC_QAF:
+ kmsan_unpoison_memory(param, sizeof(struct dfltcc_qaf_param));
+ break;
+ case DFLTCC_GDHT:
+ kmsan_unpoison_memory(param, offsetof(struct dfltcc_param_v0, csb));
+ break;
+ case DFLTCC_CMPR:
+ kmsan_unpoison_memory(param, sizeof(struct dfltcc_param_v0));
+ kmsan_unpoison_memory(
+ orig_t2,
+ t2 - orig_t2 +
+ (((struct dfltcc_param_v0 *)param)->sbb == 0 ? 0 : 1));
+ break;
+ case DFLTCC_XPND:
+ kmsan_unpoison_memory(param, sizeof(struct dfltcc_param_v0));
+ kmsan_unpoison_memory(orig_t2, t2 - orig_t2);
+ break;
+ }
+
if (op1)
*op1 = t2;
if (len1)
--
2.45.1