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view src/core/ngx_buf.h @ 6351:497d0cff8ace

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Resolver: fixed use-after-free memory accesses with CNAME. When several requests were waiting for a response, then after getting a CNAME response only the last request's context had the name updated. Contexts of other requests had the wrong name. This name was used by ngx_resolve_name_done() to find the node to remove the request context from. When the name was wrong, the request could not be properly cancelled, its context was freed but stayed linked to the node's waiting list. This happened e.g. when the first request was aborted or timed out before the resolving completed. When it completed, this triggered a use-after-free memory access by calling ctx->handler of already freed request context. The bug manifests itself by "could not cancel <name> resolving" alerts in error_log. When a request was responded with a CNAME, the request context kept the pointer to the original node's rn->u.cname. If the original node expired before the resolving timed out or completed with an error, this would trigger a use-after-free memory access via ctx->name in ctx->handler(). The fix is to keep ctx->name unmodified. The name from context is no longer used by ngx_resolve_name_done(). Instead, we now keep the pointer to resolver node to which this request is linked. Keeping the original name intact also improves logging.
author Roman Arutyunyan <arut@nginx.com>
date Tue, 26 Jan 2016 16:46:59 +0300
parents 1fdba317ee6d
children e8d4c9e9682a
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_BUF_H_INCLUDED_
#define _NGX_BUF_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>


typedef void *            ngx_buf_tag_t;

typedef struct ngx_buf_s  ngx_buf_t;

struct ngx_buf_s {
    u_char          *pos;
    u_char          *last;
    off_t            file_pos;
    off_t            file_last;

    u_char          *start;         /* start of buffer */
    u_char          *end;           /* end of buffer */
    ngx_buf_tag_t    tag;
    ngx_file_t      *file;
    ngx_buf_t       *shadow;


    /* the buf's content could be changed */
    unsigned         temporary:1;

    /*
     * the buf's content is in a memory cache or in a read only memory
     * and must not be changed
     */
    unsigned         memory:1;

    /* the buf's content is mmap()ed and must not be changed */
    unsigned         mmap:1;

    unsigned         recycled:1;
    unsigned         in_file:1;
    unsigned         flush:1;
    unsigned         sync:1;
    unsigned         last_buf:1;
    unsigned         last_in_chain:1;

    unsigned         last_shadow:1;
    unsigned         temp_file:1;

    /* STUB */ int   num;
};


struct ngx_chain_s {
    ngx_buf_t    *buf;
    ngx_chain_t  *next;
};


typedef struct {
    ngx_int_t    num;
    size_t       size;
} ngx_bufs_t;


typedef struct ngx_output_chain_ctx_s  ngx_output_chain_ctx_t;

typedef ngx_int_t (*ngx_output_chain_filter_pt)(void *ctx, ngx_chain_t *in);

#if (NGX_HAVE_FILE_AIO)
typedef void (*ngx_output_chain_aio_pt)(ngx_output_chain_ctx_t *ctx,
    ngx_file_t *file);
#endif

struct ngx_output_chain_ctx_s {
    ngx_buf_t                   *buf;
    ngx_chain_t                 *in;
    ngx_chain_t                 *free;
    ngx_chain_t                 *busy;

    unsigned                     sendfile:1;
    unsigned                     directio:1;
#if (NGX_HAVE_ALIGNED_DIRECTIO)
    unsigned                     unaligned:1;
#endif
    unsigned                     need_in_memory:1;
    unsigned                     need_in_temp:1;
#if (NGX_HAVE_FILE_AIO || NGX_THREADS)
    unsigned                     aio:1;
#endif

#if (NGX_HAVE_FILE_AIO)
    ngx_output_chain_aio_pt      aio_handler;
#if (NGX_HAVE_AIO_SENDFILE)
    ssize_t                    (*aio_preload)(ngx_buf_t *file);
#endif
#endif

#if (NGX_THREADS)
    ngx_int_t                  (*thread_handler)(ngx_thread_task_t *task,
                                                 ngx_file_t *file);
    ngx_thread_task_t           *thread_task;
#endif

    off_t                        alignment;

    ngx_pool_t                  *pool;
    ngx_int_t                    allocated;
    ngx_bufs_t                   bufs;
    ngx_buf_tag_t                tag;

    ngx_output_chain_filter_pt   output_filter;
    void                        *filter_ctx;
};


typedef struct {
    ngx_chain_t                 *out;
    ngx_chain_t                **last;
    ngx_connection_t            *connection;
    ngx_pool_t                  *pool;
    off_t                        limit;
} ngx_chain_writer_ctx_t;


#define NGX_CHAIN_ERROR     (ngx_chain_t *) NGX_ERROR


#define ngx_buf_in_memory(b)        (b->temporary || b->memory || b->mmap)
#define ngx_buf_in_memory_only(b)   (ngx_buf_in_memory(b) && !b->in_file)

#define ngx_buf_special(b)                                                   \
    ((b->flush || b->last_buf || b->sync)                                    \
     && !ngx_buf_in_memory(b) && !b->in_file)

#define ngx_buf_sync_only(b)                                                 \
    (b->sync                                                                 \
     && !ngx_buf_in_memory(b) && !b->in_file && !b->flush && !b->last_buf)

#define ngx_buf_size(b)                                                      \
    (ngx_buf_in_memory(b) ? (off_t) (b->last - b->pos):                      \
                            (b->file_last - b->file_pos))

ngx_buf_t *ngx_create_temp_buf(ngx_pool_t *pool, size_t size);
ngx_chain_t *ngx_create_chain_of_bufs(ngx_pool_t *pool, ngx_bufs_t *bufs);


#define ngx_alloc_buf(pool)  ngx_palloc(pool, sizeof(ngx_buf_t))
#define ngx_calloc_buf(pool) ngx_pcalloc(pool, sizeof(ngx_buf_t))

ngx_chain_t *ngx_alloc_chain_link(ngx_pool_t *pool);
#define ngx_free_chain(pool, cl)                                             \
    cl->next = pool->chain;                                                  \
    pool->chain = cl



ngx_int_t ngx_output_chain(ngx_output_chain_ctx_t *ctx, ngx_chain_t *in);
ngx_int_t ngx_chain_writer(void *ctx, ngx_chain_t *in);

ngx_int_t ngx_chain_add_copy(ngx_pool_t *pool, ngx_chain_t **chain,
    ngx_chain_t *in);
ngx_chain_t *ngx_chain_get_free_buf(ngx_pool_t *p, ngx_chain_t **free);
void ngx_chain_update_chains(ngx_pool_t *p, ngx_chain_t **free,
    ngx_chain_t **busy, ngx_chain_t **out, ngx_buf_tag_t tag);

off_t ngx_chain_coalesce_file(ngx_chain_t **in, off_t limit);

ngx_chain_t *ngx_chain_update_sent(ngx_chain_t *in, off_t sent);

#endif /* _NGX_BUF_H_INCLUDED_ */