[MINOR] buffer_replace2 must never change the ->w entry

This function is used to move data which is located between ->w and ->r,
so it must not touch ->w, otherwise it will displace pending data which
is before the one we're actually overwriting. The issue arose in 1.4 with
some pipelined responses which cause some part of the previous one to
be chopped off when removing the connection: close header, thus
corrupting last response and shifting next one. Those are detected
in the logs because the next response will be a 502 with flags PH.

Note that this does not affect 1.3, still this is a bug that's better
fixed than blindly copy-pasted and woken up again.

(cherry picked from commit bbfa7938bd74adbfa435f26503fc10f5938195a3)

diff --git a/src/buffers.c b/src/buffers.c
index 0910320f6fcf87182c632ffcde4a0b92872ffaf1..db84327fb956c8e5141f9615926942e575c1f290 100644 (file)
--- a/src/buffers.c
+++ b/src/buffers.c
@@ -98,7 +98,7 @@ int buffer_write_chunk(struct buffer *buf, struct chunk *chunk)
 /*
  * this function writes the string <str> at position <pos> which must be in buffer <b>,
  * and moves <end> just after the end of <str>.
- * <b>'s parameters (l, r, w, h, lr) are recomputed to be valid after the shift.
+ * <b>'s parameters (l, r, lr) are recomputed to be valid after the shift.
  * the shift value (positive or negative) is returned.
  * If there's no space left, the move is not done.
  *
@@ -114,6 +114,9 @@ int buffer_replace(struct buffer *b, char *pos, char *end, const char *str)
        if (delta + b->r >= b->data + BUFSIZE)
                return 0;  /* no space left */
 
+       if (delta + b->r > b->w && b->w >= b->r && b->l)
+               return 0;  /* no space left before wrapping data */
+
        /* first, protect the end of the buffer */
        memmove(end + delta, end, b->r - end);
 
@@ -122,7 +125,6 @@ int buffer_replace(struct buffer *b, char *pos, char *end, const char *str)
 
        /* we only move data after the displaced zone */
        if (b->r  > pos) b->r  += delta;
-       if (b->w  > pos) b->w  += delta;
        if (b->lr > pos) b->lr += delta;
        b->l += delta;
 
@@ -148,6 +150,9 @@ int buffer_replace2(struct buffer *b, char *pos, char *end, const char *str, int
        if (delta + b->r >= b->data + BUFSIZE)
                return 0;  /* no space left */
 
+       if (delta + b->r > b->w && b->w >= b->r && b->l)
+               return 0;  /* no space left before wrapping data */
+
        /* first, protect the end of the buffer */
        memmove(end + delta, end, b->r - end);
 
@@ -157,7 +162,6 @@ int buffer_replace2(struct buffer *b, char *pos, char *end, const char *str, int
 
        /* we only move data after the displaced zone */
        if (b->r  > pos) b->r  += delta;
-       if (b->w  > pos) b->w  += delta;
        if (b->lr > pos) b->lr += delta;
        b->l += delta;