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[75.142.250.213]) by smtp.gmail.com with ESMTPSA id s66sm9182400ooa.37.2020.12.30.06.56.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Dec 2020 06:56:09 -0800 (PST) From: trix@redhat.com To: dwmw2@infradead.org, richard@nod.at, natechancellor@gmail.com, ndesaulniers@google.com Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Tom Rix Subject: [PATCH] jffs2: fix use after free in jffs2_sum_write_data() Date: Wed, 30 Dec 2020 06:56:04 -0800 Message-Id: <20201230145604.1586486-1-trix@redhat.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tom Rix clang static analysis reports this problem fs/jffs2/summary.c:794:31: warning: Use of memory after it is freed c->summary->sum_list_head = temp->u.next; ^~~~~~~~~~~~ In jffs2_sum_write_data(), in a loop summary data is handles a node at a time. When it has written out the node it is removed the summary list, and the node is deleted. In the corner case when a JFFS2_FEATURE_RWCOMPAT_COPY is seen, a call is made to jffs2_sum_disable_collecting(). jffs2_sum_disable_collecting() deletes the whole list which conflicts with the loop's deleting the list by parts. To preserve the old behavior of stopping the write midway, bail out of the loop after disabling summary collection. Fixes: 6171586a7ae5 ("[JFFS2] Correct handling of JFFS2_FEATURE_RWCOMPAT_COPY nodes.") Signed-off-by: Tom Rix --- fs/jffs2/summary.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/jffs2/summary.c b/fs/jffs2/summary.c index be7c8a6a5748..4fe64519870f 100644 --- a/fs/jffs2/summary.c +++ b/fs/jffs2/summary.c @@ -783,6 +783,8 @@ static int jffs2_sum_write_data(struct jffs2_sb_info *c, struct jffs2_eraseblock dbg_summary("Writing unknown RWCOMPAT_COPY node type %x\n", je16_to_cpu(temp->u.nodetype)); jffs2_sum_disable_collecting(c->summary); + /* The above call removes the list, nothing more to do */ + goto bail_rwcompat; } else { BUG(); /* unknown node in summary information */ } @@ -794,6 +796,7 @@ static int jffs2_sum_write_data(struct jffs2_sb_info *c, struct jffs2_eraseblock c->summary->sum_num--; } + bail_rwcompat: jffs2_sum_reset_collected(c->summary); -- 2.27.0