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zstd: cap buffer at max instead of aborting on overshoot [Backport to 4.2] #11900

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Merged
cosmo0920 merged 1 commit into from
Jun 3, 2026
Merged

zstd: cap buffer at max instead of aborting on overshoot [Backport to 4.2] #11900

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18 changes: 17 additions & 1 deletion src/flb_zstd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,8 @@ struct flb_zstd_decompression_context {
ZSTD_DCtx *dctx;
};

#define FLB_ZSTD_DEFAULT_CHUNK 64 * 1024 /* 64 KB buffer */
#define FLB_ZSTD_DEFAULT_CHUNK (64 * 1024) /* 64 KB buffer */
#define FLB_ZSTD_DECOMPRESS_MAX (100 * 1024 * 1024) /* 100 MB limit */

int flb_zstd_compress(void *in_data, size_t in_len, void **out_data, size_t *out_len)
{
Expand Down Expand Up @@ -104,7 +105,16 @@ static int zstd_uncompress_unknown_size(void *in_data, size_t in_len, void **out

/* check if we need more space */
if (output.pos == out_size) {
if (out_size >= FLB_ZSTD_DECOMPRESS_MAX) {
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@chatgpt-codex-connector chatgpt-codex-connector Bot Jun 3, 2026

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P2 Badge Allow exact-size unknown zstd frames

For frames with ZSTD_CONTENTSIZE_UNKNOWN, this rejects a valid payload whose decompressed size is exactly FLB_ZSTD_DECOMPRESS_MAX: after the final ZSTD_decompressStream() call fills the 100 MB buffer, ret can already be 0, but this check runs before the existing ret == 0 completion check and returns failure. Known-size frames of exactly 100 MB are accepted by the new size > FLB_ZSTD_DECOMPRESS_MAX guard, so the limit is inconsistent and unknown-size inputs at the documented maximum are unnecessarily dropped.

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flb_error("[zstd] maximum decompression size reached (~100 MB)");
flb_free(buf);
ZSTD_freeDCtx(dctx);
return -1;
}
out_size *= 2;
if (out_size > FLB_ZSTD_DECOMPRESS_MAX) {
out_size = FLB_ZSTD_DECOMPRESS_MAX;
}
tmp = flb_realloc(buf, out_size);
if (!tmp) {
flb_errno();
Expand Down Expand Up @@ -146,6 +156,12 @@ int flb_zstd_uncompress(void *in_data, size_t in_len, void **out_data, size_t *o
return ret;
}

if (size > FLB_ZSTD_DECOMPRESS_MAX) {
flb_error("[zstd] maximum decompression size is %d bytes",
FLB_ZSTD_DECOMPRESS_MAX);
return -1;
}

buf = flb_malloc(size);
if (!buf) {
flb_errno();
Expand Down
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