From eae8d82529dd9820e206ecba0047b806c4410e65 Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Mon, 6 Nov 2017 10:43:18 +0800
Subject: [PATCH] btrfs: Fix wild memory access in compression level parser
[BUG]
Kernel panic when mounting with "-o compress" mount option.
KASAN will report like:
------
==================================================================
BUG: KASAN: wild-memory-access in strncmp+0x31/0xc0
Read of size 1 at addr d86735fce994f800 by task mount/662
...
Call Trace:
dump_stack+0xe3/0x175
kasan_report+0x163/0x370
__asan_load1+0x47/0x50
strncmp+0x31/0xc0
btrfs_compress_str2level+0x20/0x70 [btrfs]
btrfs_parse_options+0xff4/0x1870 [btrfs]
open_ctree+0x2679/0x49f0 [btrfs]
btrfs_mount+0x1b7f/0x1d30 [btrfs]
mount_fs+0x49/0x190
vfs_kern_mount.part.29+0xba/0x280
vfs_kern_mount+0x13/0x20
btrfs_mount+0x31e/0x1d30 [btrfs]
mount_fs+0x49/0x190
vfs_kern_mount.part.29+0xba/0x280
do_mount+0xaad/0x1a00
SyS_mount+0x98/0xe0
entry_SYSCALL_64_fastpath+0x1f/0xbe
------
[Cause]
For 'compress' and 'compress_force' options, its token doesn't expect
any parameter so its args[0] contains uninitialized data.
Accessing args[0] will cause above wild memory access.
[Fix]
For Opt_compress and Opt_compress_force, set compression level to
the default.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ set the default in advance ]
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/compression.c | 2 +-
fs/btrfs/compression.h | 2 ++
fs/btrfs/super.c | 13 +++++++++++--
3 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 4a78e5726337..5982c8a71f02 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1529,5 +1529,5 @@ unsigned int btrfs_compress_str2level(const char *str)
if (str[4] == ':' && '1' <= str[5] && str[5] <= '9' && str[6] == 0)
return str[5] - '0';
- return 0;
+ return BTRFS_ZLIB_DEFAULT_LEVEL;
}
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 93c5b82ae97e..0868cc554f14 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -34,6 +34,8 @@
/* Maximum size of data before compression */
#define BTRFS_MAX_UNCOMPRESSED (SZ_128K)
+#define BTRFS_ZLIB_DEFAULT_LEVEL 3
+
struct compressed_bio {
/* number of bios pending for this compressed extent */
refcount_t pending_bios;
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 65af029559b5..ff3545e526f5 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -507,9 +507,18 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
token == Opt_compress_force ||
strncmp(args[0].from, "zlib", 4) == 0) {
compress_type = "zlib";
+
info->compress_type = BTRFS_COMPRESS_ZLIB;
- info->compress_level =
- btrfs_compress_str2level(args[0].from);
+ info->compress_level = BTRFS_ZLIB_DEFAULT_LEVEL;
+ /*
+ * args[0] contains uninitialized data since
+ * for these tokens we don't expect any
+ * parameter.
+ */
+ if (token != Opt_compress &&
+ token != Opt_compress_force)
+ info->compress_level =
+ btrfs_compress_str2level(args[0].from);
btrfs_set_opt(info->mount_opt, COMPRESS);
btrfs_clear_opt(info->mount_opt, NODATACOW);
btrfs_clear_opt(info->mount_opt, NODATASUM);