linux-kernel - [PATCH 5/8] lib/zlib: DFLTCC not writing header bits when avail

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Date:   Thu, 26 Jan 2023 14:14:25 +0100
From:   Mikhail Zaslonko <zaslonko@...ux.ibm.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Mikhail Zaslonko <zaslonko@...ux.ibm.com>
Subject: [PATCH 5/8] lib/zlib: DFLTCC not writing header bits when avail_out == 0

This commit is based on:
  https://github.com/zlib-ng/zlib-ng/commit/ce409c6

Signed-off-by: Mikhail Zaslonko <zaslonko@...ux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 lib/zlib_dfltcc/dfltcc_deflate.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/lib/zlib_dfltcc/dfltcc_deflate.c b/lib/zlib_dfltcc/dfltcc_deflate.c
index 211d344710d5..d4c92f99808e 100644
--- a/lib/zlib_dfltcc/dfltcc_deflate.c
+++ b/lib/zlib_dfltcc/dfltcc_deflate.c
@@ -170,13 +170,18 @@ int dfltcc_deflate(
             param->bcf = 0;
             dfltcc_state->block_threshold =
                 strm->total_in + dfltcc_state->block_size;
-            if (strm->avail_out == 0) {
-                *result = need_more;
-                return 1;
-            }
         }
     }
 
+    /* No space for compressed data. If we proceed, dfltcc_cmpr() will return
+     * DFLTCC_CC_OP1_TOO_SHORT without buffering header bits, but we will still
+     * set BCF=1, which is wrong. Avoid complications and return early.
+     */
+    if (strm->avail_out == 0) {
+        *result = need_more;
+        return 1;
+    }
+
     /* The caller gave us too much data. Pass only one block worth of
      * uncompressed data to DFLTCC and mask the rest, so that on the next
      * iteration we start a new block.
-- 
2.34.1