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BUG/MEDIUM: htx: Fix a possible null derefs in htx_xfer_blks()

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In htx_xfer_blks() function, when headers or trailers are partially
transferred, we rollback the copy by removing copied blocks. Internally, all
blocks between <dstref> and <dstblk> are removed. But if the transfer was
stopped because we failed to reserve a block, the variable <dstblk> is
NULL. Thus, we must not try to remove it. It is unexpected to call
htx_remove_blk() in this case.

htx_remove_blk() was updated to test <blk> variable inside the existing
BUG_ON(). The block must be defined.

For now, this bug may only be encountered when H2 trailers are copied. On H2
headers, the destination buffer is empty. Thus a swap is performed.

This patch should fix the issue #1578. It must be backported as far as 2.4.
This commit is contained in:
Christopher Faulet 2022-02-28 15:29:56 +01:00
parent 4ab8438362
commit 234a10aa9b
1 changed files with 6 additions and 4 deletions
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10
src/htx.c
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@ -336,7 +336,7 @@ struct htx_blk *htx_remove_blk(struct htx *htx, struct htx_blk *blk)
enum htx_blk_type type;
uint32_t pos, addr, sz;
BUG_ON(htx->head == -1);
BUG_ON(!blk || htx->head == -1);
/* This is the last block in use */
if (htx->head == htx->tail) {
@ -739,12 +739,14 @@ struct htx_ret htx_xfer_blks(struct htx *dst, struct htx *src, uint32_t count,
}
if (unlikely(dstref)) {
/* Headers or trailers part was partially xferred, so rollback the copy
* by removing all block between <dstref> and <dstblk>, both included.
/* Headers or trailers part was partially xferred, so rollback
* the copy by removing all block between <dstref> and <dstblk>,
* both included. <dstblk> may be NULL.
*/
while (dstref && dstref != dstblk)
dstref = htx_remove_blk(dst, dstref);
htx_remove_blk(dst, dstblk);
if (dstblk)
htx_remove_blk(dst, dstblk);
/* <dst> HTX message is empty, it means the headers or trailers
* part is too big to be copied at once.