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Date: Tue, 29 Sep 2020 13:00:15 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Liu Song <liu.song11@....com.cn>, Richard Weinberger <richard@....at>, Sasha Levin <sashal@...nel.org> Subject: [PATCH 4.9 071/121] ubifs: Fix out-of-bounds memory access caused by abnormal value of node_len From: Liu Song <liu.song11@....com.cn> [ Upstream commit acc5af3efa303d5f36cc8c0f61716161f6ca1384 ] In “ubifs_check_node”, when the value of "node_len" is abnormal, the code will goto label of "out_len" for execution. Then, in the following "ubifs_dump_node", if inode type is "UBIFS_DATA_NODE", in "print_hex_dump", an out-of-bounds access may occur due to the wrong "ch->len". Therefore, when the value of "node_len" is abnormal, data length should to be adjusted to a reasonable safe range. At this time, structured data is not credible, so dump the corrupted data directly for analysis. Signed-off-by: Liu Song <liu.song11@....com.cn> Signed-off-by: Richard Weinberger <richard@....at> Signed-off-by: Sasha Levin <sashal@...nel.org> --- fs/ubifs/io.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c index 97be412153328..9213a9e046ae0 100644 --- a/fs/ubifs/io.c +++ b/fs/ubifs/io.c @@ -237,7 +237,7 @@ int ubifs_is_mapped(const struct ubifs_info *c, int lnum) int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum, int offs, int quiet, int must_chk_crc) { - int err = -EINVAL, type, node_len; + int err = -EINVAL, type, node_len, dump_node = 1; uint32_t crc, node_crc, magic; const struct ubifs_ch *ch = buf; @@ -290,10 +290,22 @@ int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum, out_len: if (!quiet) ubifs_err(c, "bad node length %d", node_len); + if (type == UBIFS_DATA_NODE && node_len > UBIFS_DATA_NODE_SZ) + dump_node = 0; out: if (!quiet) { ubifs_err(c, "bad node at LEB %d:%d", lnum, offs); - ubifs_dump_node(c, buf); + if (dump_node) { + ubifs_dump_node(c, buf); + } else { + int safe_len = min3(node_len, c->leb_size - offs, + (int)UBIFS_MAX_DATA_NODE_SZ); + pr_err("\tprevent out-of-bounds memory access\n"); + pr_err("\ttruncated data node length %d\n", safe_len); + pr_err("\tcorrupted data node:\n"); + print_hex_dump(KERN_ERR, "\t", DUMP_PREFIX_OFFSET, 32, 1, + buf, safe_len, 0); + } dump_stack(); } return err; -- 2.25.1
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