From eae8d82529dd9820e206ecba0047b806c4410e65 Mon Sep 17 00:00:00 2001 From: Qu Wenruo 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 Reviewed-by: David Sterba [ set the default in advance ] Signed-off-by: David Sterba --- 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);