linux-kernel - [PATCH] lib/xz: Fix XZ_DYNALLOC to avoid useless memory reallocations

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Message-ID: <20191104185107.3b6330df@tukaani.org>
Date:   Mon, 4 Nov 2019 18:51:07 +0200
From:   Lasse Collin <lasse.collin@...aani.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, "Yu Sun (yusun2)" <yusun2@...co.com>,
        "Yixia Si (yisi)" <yisi@...co.com>
Subject: [PATCH] lib/xz: Fix XZ_DYNALLOC to avoid useless memory
 reallocations

From: Lasse Collin <lasse.collin@...aani.org>

s->dict.allocated was initialized to 0 but never set after a successful
allocation, thus the code always thought that the dictionary buffer has
to be reallocated.

Signed-off-by: Lasse Collin <lasse.collin@...aani.org>
Reported-by: Yu Sun <yusun2@...co.com>
---

diff -Nrup linux-5.3-vanilla/lib/xz/xz_dec_lzma2.c linux-5.3/lib/xz/xz_dec_lzma2.c
--- linux-5.3-vanilla/lib/xz/xz_dec_lzma2.c	2019-09-16 00:19:32.000000000 +0300
+++ linux-5.3/lib/xz/xz_dec_lzma2.c	2019-10-30 20:33:15.460857851 +0200
@@ -1146,6 +1146,7 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_reset
 
 		if (DEC_IS_DYNALLOC(s->dict.mode)) {
 			if (s->dict.allocated < s->dict.size) {
+				s->dict.allocated = s->dict.size;
 				vfree(s->dict.buf);
 				s->dict.buf = vmalloc(s->dict.size);
 				if (s->dict.buf == NULL) {