Commit aa7145c1 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller

bpf, events: fix offset in skb copy handler

This patch fixes the __output_custom() routine we currently use with
bpf_skb_copy(). I missed that when len is larger than the size of the
current handle, we can issue multiple invocations of copy_func, and
__output_custom() advances destination but also source buffer by the
written amount of bytes. When we have __output_custom(), this is actually
wrong since in that case the source buffer points to a non-linear object,
in our case an skb, which the copy_func helper is supposed to walk.
Therefore, since this is non-linear we thus need to pass the offset into
the helper, so that copy_func can use it for extracting the data from
the source object.

Therefore, adjust the callback signatures properly and pass offset
into the skb_header_pointer() invoked from bpf_skb_copy() callback. The
__DEFINE_OUTPUT_COPY_BODY() is adjusted to accommodate for two things:
i) to pass in whether we should advance source buffer or not; this is
a compile-time constant condition, ii) to pass in the offset for
__output_custom(), which we do with help of __VA_ARGS__, so everything
can stay inlined as is currently. Both changes allow for adapting the
__output_* fast-path helpers w/o extra overhead.

Fixes: 555c8a86 ("bpf: avoid stack copy and use skb ctx for event output")
Fixes: 7e3f977e ("perf, events: add non-linear data support for raw records")
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a1b43edd
......@@ -211,7 +211,7 @@ bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *f
const struct bpf_func_proto *bpf_get_trace_printk_proto(void);
typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const void *src,
unsigned long len);
unsigned long off, unsigned long len);
u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy);
......
......@@ -70,7 +70,7 @@ struct perf_callchain_entry_ctx {
};
typedef unsigned long (*perf_copy_f)(void *dst, const void *src,
unsigned long len);
unsigned long off, unsigned long len);
struct perf_raw_frag {
union {
......
......@@ -123,18 +123,19 @@ static inline unsigned long perf_aux_size(struct ring_buffer *rb)
return rb->aux_nr_pages << PAGE_SHIFT;
}
#define __DEFINE_OUTPUT_COPY_BODY(memcpy_func) \
#define __DEFINE_OUTPUT_COPY_BODY(advance_buf, memcpy_func, ...) \
{ \
unsigned long size, written; \
\
do { \
size = min(handle->size, len); \
written = memcpy_func(handle->addr, buf, size); \
written = memcpy_func(__VA_ARGS__); \
written = size - written; \
\
len -= written; \
handle->addr += written; \
buf += written; \
if (advance_buf) \
buf += written; \
handle->size -= written; \
if (!handle->size) { \
struct ring_buffer *rb = handle->rb; \
......@@ -153,12 +154,16 @@ static inline unsigned long perf_aux_size(struct ring_buffer *rb)
static inline unsigned long \
func_name(struct perf_output_handle *handle, \
const void *buf, unsigned long len) \
__DEFINE_OUTPUT_COPY_BODY(memcpy_func)
__DEFINE_OUTPUT_COPY_BODY(true, memcpy_func, handle->addr, buf, size)
static inline unsigned long
__output_custom(struct perf_output_handle *handle, perf_copy_f copy_func,
const void *buf, unsigned long len)
__DEFINE_OUTPUT_COPY_BODY(copy_func)
{
unsigned long orig_len = len;
__DEFINE_OUTPUT_COPY_BODY(false, copy_func, handle->addr, buf,
orig_len - len, size)
}
static inline unsigned long
memcpy_common(void *dst, const void *src, unsigned long n)
......
......@@ -2026,9 +2026,9 @@ bool bpf_helper_changes_skb_data(void *func)
}
static unsigned long bpf_skb_copy(void *dst_buff, const void *skb,
unsigned long len)
unsigned long off, unsigned long len)
{
void *ptr = skb_header_pointer(skb, 0, len, dst_buff);
void *ptr = skb_header_pointer(skb, off, len, dst_buff);
if (unlikely(!ptr))
return len;
......
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