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linux-stable/include/net/strparser.h
Jussi Maki b2c4618162 bpf, sockmap: sk_skb data_end access incorrect when src_reg = dst_reg 
The current conversion of skb->data_end reads like this:

  ; data_end = (void*)(long)skb->data_end;
   559: (79) r1 = *(u64 *)(r2 +200)   ; r1  = skb->data
   560: (61) r11 = *(u32 *)(r2 +112)  ; r11 = skb->len
   561: (0f) r1 += r11
   562: (61) r11 = *(u32 *)(r2 +116)
   563: (1f) r1 -= r11

But similar to the case in 84f44df664 ("bpf: sock_ops sk access may stomp
registers when dst_reg = src_reg"), the code will read an incorrect skb->len
when src == dst. In this case we end up generating this xlated code:

  ; data_end = (void*)(long)skb->data_end;
   559: (79) r1 = *(u64 *)(r1 +200)   ; r1  = skb->data
   560: (61) r11 = *(u32 *)(r1 +112)  ; r11 = (skb->data)->len
   561: (0f) r1 += r11
   562: (61) r11 = *(u32 *)(r1 +116)
   563: (1f) r1 -= r11

... where line 560 is the reading 4B of (skb->data + 112) instead of the
intended skb->len Here the skb pointer in r1 gets set to skb->data and the
later deref for skb->len ends up following skb->data instead of skb.

This fixes the issue similarly to the patch mentioned above by creating an
additional temporary variable and using to store the register when dst_reg =
src_reg. We name the variable bpf_temp_reg and place it in the cb context for
sk_skb. Then we restore from the temp to ensure nothing is lost.

Fixes: 16137b09a6 ("bpf: Compute data_end dynamically with JIT code")
Signed-off-by: Jussi Maki <joamaki@gmail.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20211103204736.248403-6-john.fastabend@gmail.com
2021-11-09 01:05:34 +01:00

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Stream Parser
*
* Copyright (c) 2016 Tom Herbert <tom@herbertland.com>
*/
#ifndef __NET_STRPARSER_H_
#define __NET_STRPARSER_H_
#include <linux/skbuff.h>
#include <net/sock.h>
#define STRP_STATS_ADD(stat, count) ((stat) += (count))
#define STRP_STATS_INCR(stat) ((stat)++)
struct strp_stats {
unsigned long long msgs;
unsigned long long bytes;
unsigned int mem_fail;
unsigned int need_more_hdr;
unsigned int msg_too_big;
unsigned int msg_timeouts;
unsigned int bad_hdr_len;
};
struct strp_aggr_stats {
unsigned long long msgs;
unsigned long long bytes;
unsigned int mem_fail;
unsigned int need_more_hdr;
unsigned int msg_too_big;
unsigned int msg_timeouts;
unsigned int bad_hdr_len;
unsigned int aborts;
unsigned int interrupted;
unsigned int unrecov_intr;
};
struct strparser;
/* Callbacks are called with lock held for the attached socket */
struct strp_callbacks {
int (*parse_msg)(struct strparser *strp, struct sk_buff *skb);
void (*rcv_msg)(struct strparser *strp, struct sk_buff *skb);
int (*read_sock_done)(struct strparser *strp, int err);
void (*abort_parser)(struct strparser *strp, int err);
void (*lock)(struct strparser *strp);
void (*unlock)(struct strparser *strp);
};
struct strp_msg {
int full_len;
int offset;
};
struct _strp_msg {
/* Internal cb structure. struct strp_msg must be first for passing
* to upper layer.
*/
struct strp_msg strp;
int accum_len;
};
struct sk_skb_cb {
#define SK_SKB_CB_PRIV_LEN 20
unsigned char data[SK_SKB_CB_PRIV_LEN];
struct _strp_msg strp;
/* temp_reg is a temporary register used for bpf_convert_data_end_access
* when dst_reg == src_reg.
*/
u64 temp_reg;
};
static inline struct strp_msg *strp_msg(struct sk_buff *skb)
{
return (struct strp_msg *)((void *)skb->cb +
offsetof(struct sk_skb_cb, strp));
}
/* Structure for an attached lower socket */
struct strparser {
struct sock *sk;
u32 stopped : 1;
u32 paused : 1;
u32 aborted : 1;
u32 interrupted : 1;
u32 unrecov_intr : 1;
struct sk_buff **skb_nextp;
struct sk_buff *skb_head;
unsigned int need_bytes;
struct delayed_work msg_timer_work;
struct work_struct work;
struct strp_stats stats;
struct strp_callbacks cb;
};
/* Must be called with lock held for attached socket */
static inline void strp_pause(struct strparser *strp)
{
strp->paused = 1;
}
/* May be called without holding lock for attached socket */
void strp_unpause(struct strparser *strp);
/* Must be called with process lock held (lock_sock) */
void __strp_unpause(struct strparser *strp);
static inline void save_strp_stats(struct strparser *strp,
struct strp_aggr_stats *agg_stats)
{
/* Save psock statistics in the mux when psock is being unattached. */
#define SAVE_PSOCK_STATS(_stat) (agg_stats->_stat += \
strp->stats._stat)
SAVE_PSOCK_STATS(msgs);
SAVE_PSOCK_STATS(bytes);
SAVE_PSOCK_STATS(mem_fail);
SAVE_PSOCK_STATS(need_more_hdr);
SAVE_PSOCK_STATS(msg_too_big);
SAVE_PSOCK_STATS(msg_timeouts);
SAVE_PSOCK_STATS(bad_hdr_len);
#undef SAVE_PSOCK_STATS
if (strp->aborted)
agg_stats->aborts++;
if (strp->interrupted)
agg_stats->interrupted++;
if (strp->unrecov_intr)
agg_stats->unrecov_intr++;
}
static inline void aggregate_strp_stats(struct strp_aggr_stats *stats,
struct strp_aggr_stats *agg_stats)
{
#define SAVE_PSOCK_STATS(_stat) (agg_stats->_stat += stats->_stat)
SAVE_PSOCK_STATS(msgs);
SAVE_PSOCK_STATS(bytes);
SAVE_PSOCK_STATS(mem_fail);
SAVE_PSOCK_STATS(need_more_hdr);
SAVE_PSOCK_STATS(msg_too_big);
SAVE_PSOCK_STATS(msg_timeouts);
SAVE_PSOCK_STATS(bad_hdr_len);
SAVE_PSOCK_STATS(aborts);
SAVE_PSOCK_STATS(interrupted);
SAVE_PSOCK_STATS(unrecov_intr);
#undef SAVE_PSOCK_STATS
}
void strp_done(struct strparser *strp);
void strp_stop(struct strparser *strp);
void strp_check_rcv(struct strparser *strp);
int strp_init(struct strparser *strp, struct sock *sk,
const struct strp_callbacks *cb);
void strp_data_ready(struct strparser *strp);
int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
unsigned int orig_offset, size_t orig_len,
size_t max_msg_size, long timeo);
#endif /* __NET_STRPARSER_H_ */
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