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BUG/MINOR: shctx: fix shctx_row_data_get() when offset exceeds a block

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The loop advanced the block pointer only after the copy, but skipped
blocks preceding <offset> with a continue, which bypassed that advance.
As a result any read starting past the first block copied nothing.

This notably affects conditional requests: should_send_notmodified_response()
reads the stored ETag at entry->etag_offset, so a cached response whose
ETag header sits beyond the first block fails revalidation and is served
in full (200) instead of 304.

Rewrite the loop as a for() so the block pointer always advances,
regardless of whether the current block is copied or skipped.

This should be backported as far as 2.6.
This commit is contained in:
Maxime Henrion 2026-07-08 12:37:07 -04:00 committed by Willy Tarreau
parent f34517a1aa
commit 6750c36adf
1 changed files with 8 additions and 18 deletions
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26
src/shctx.c
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@ -226,30 +226,22 @@ int shctx_row_data_append(struct shared_context *shctx, struct shared_block *fir
int shctx_row_data_get(struct shared_context *shctx, struct shared_block *first,
unsigned char *dst, int offset, int len)
{
int count = 0, size = 0, start = -1;
int count, size, start = -1;
struct shared_block *block;
/* can't copy more */
if (len > first->len)
len = first->len;
block = first;
count = 0;
/* Pass through the blocks to copy them */
do {
if (count >= first->block_count || len <= 0)
break;
count++;
/* continue until we are in right block
corresponding to the offset */
if (count < offset / shctx->block_size + 1)
/* Walk the blocks, skipping those that precede the one holding <offset>. */
for (block = first, count = 0; count < first->block_count && len > 0;
block = LIST_ELEM(block->list.n, struct shared_block *, list), count++) {
if (count < offset / shctx->block_size)
continue;
/* on the first block, data won't possibly began at offset 0 */
/* the first copied block may not start at its beginning */
if (start == -1)
start = offset - (count - 1) * shctx->block_size;
start = offset - count * shctx->block_size;
BUG_ON(start < 0);
/* size can be lower than a block when copying the last block */
@ -260,9 +252,7 @@ int shctx_row_data_get(struct shared_context *shctx, struct shared_block *first,
dst += size;
len -= size;
start = 0;
block = LIST_ELEM(block->list.n, struct shared_block*, list);
} while (block != first);
}
return len;
}