lkml.org 
[lkml]   [2019]   [Jul]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.2 367/413] btrfs: correctly validate compression type
    Date
    From: Johannes Thumshirn <jthumshirn@suse.de>

    commit aa53e3bfac7205fb3a8815ac1c937fd6ed01b41e upstream.

    Nikolay reported the following KASAN splat when running btrfs/048:

    [ 1843.470920] ==================================================================
    [ 1843.471971] BUG: KASAN: slab-out-of-bounds in strncmp+0x66/0xb0
    [ 1843.472775] Read of size 1 at addr ffff888111e369e2 by task btrfs/3979

    [ 1843.473904] CPU: 3 PID: 3979 Comm: btrfs Not tainted 5.2.0-rc3-default #536
    [ 1843.475009] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
    [ 1843.476322] Call Trace:
    [ 1843.476674] dump_stack+0x7c/0xbb
    [ 1843.477132] ? strncmp+0x66/0xb0
    [ 1843.477587] print_address_description+0x114/0x320
    [ 1843.478256] ? strncmp+0x66/0xb0
    [ 1843.478740] ? strncmp+0x66/0xb0
    [ 1843.479185] __kasan_report+0x14e/0x192
    [ 1843.479759] ? strncmp+0x66/0xb0
    [ 1843.480209] kasan_report+0xe/0x20
    [ 1843.480679] strncmp+0x66/0xb0
    [ 1843.481105] prop_compression_validate+0x24/0x70
    [ 1843.481798] btrfs_xattr_handler_set_prop+0x65/0x160
    [ 1843.482509] __vfs_setxattr+0x71/0x90
    [ 1843.483012] __vfs_setxattr_noperm+0x84/0x130
    [ 1843.483606] vfs_setxattr+0xac/0xb0
    [ 1843.484085] setxattr+0x18c/0x230
    [ 1843.484546] ? vfs_setxattr+0xb0/0xb0
    [ 1843.485048] ? __mod_node_page_state+0x1f/0xa0
    [ 1843.485672] ? _raw_spin_unlock+0x24/0x40
    [ 1843.486233] ? __handle_mm_fault+0x988/0x1290
    [ 1843.486823] ? lock_acquire+0xb4/0x1e0
    [ 1843.487330] ? lock_acquire+0xb4/0x1e0
    [ 1843.487842] ? mnt_want_write_file+0x3c/0x80
    [ 1843.488442] ? debug_lockdep_rcu_enabled+0x22/0x40
    [ 1843.489089] ? rcu_sync_lockdep_assert+0xe/0x70
    [ 1843.489707] ? __sb_start_write+0x158/0x200
    [ 1843.490278] ? mnt_want_write_file+0x3c/0x80
    [ 1843.490855] ? __mnt_want_write+0x98/0xe0
    [ 1843.491397] __x64_sys_fsetxattr+0xba/0xe0
    [ 1843.492201] ? trace_hardirqs_off_thunk+0x1a/0x1c
    [ 1843.493201] do_syscall_64+0x6c/0x230
    [ 1843.493988] entry_SYSCALL_64_after_hwframe+0x49/0xbe
    [ 1843.495041] RIP: 0033:0x7fa7a8a7707a
    [ 1843.495819] Code: 48 8b 0d 21 de 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 be 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ee dd 2b 00 f7 d8 64 89 01 48
    [ 1843.499203] RSP: 002b:00007ffcb73bca38 EFLAGS: 00000202 ORIG_RAX: 00000000000000be
    [ 1843.500210] RAX: ffffffffffffffda RBX: 00007ffcb73bda9d RCX: 00007fa7a8a7707a
    [ 1843.501170] RDX: 00007ffcb73bda9d RSI: 00000000006dc050 RDI: 0000000000000003
    [ 1843.502152] RBP: 00000000006dc050 R08: 0000000000000000 R09: 0000000000000000
    [ 1843.503109] R10: 0000000000000002 R11: 0000000000000202 R12: 00007ffcb73bda91
    [ 1843.504055] R13: 0000000000000003 R14: 00007ffcb73bda82 R15: ffffffffffffffff

    [ 1843.505268] Allocated by task 3979:
    [ 1843.505771] save_stack+0x19/0x80
    [ 1843.506211] __kasan_kmalloc.constprop.5+0xa0/0xd0
    [ 1843.506836] setxattr+0xeb/0x230
    [ 1843.507264] __x64_sys_fsetxattr+0xba/0xe0
    [ 1843.507886] do_syscall_64+0x6c/0x230
    [ 1843.508429] entry_SYSCALL_64_after_hwframe+0x49/0xbe

    [ 1843.509558] Freed by task 0:
    [ 1843.510188] (stack is not available)

    [ 1843.511309] The buggy address belongs to the object at ffff888111e369e0
    which belongs to the cache kmalloc-8 of size 8
    [ 1843.514095] The buggy address is located 2 bytes inside of
    8-byte region [ffff888111e369e0, ffff888111e369e8)
    [ 1843.516524] The buggy address belongs to the page:
    [ 1843.517561] page:ffff88813f478d80 refcount:1 mapcount:0 mapping:ffff88811940c300 index:0xffff888111e373b8 compound_mapcount: 0
    [ 1843.519993] flags: 0x4404000010200(slab|head)
    [ 1843.520951] raw: 0004404000010200 ffff88813f48b008 ffff888119403d50 ffff88811940c300
    [ 1843.522616] raw: ffff888111e373b8 000000000016000f 00000001ffffffff 0000000000000000
    [ 1843.524281] page dumped because: kasan: bad access detected

    [ 1843.525936] Memory state around the buggy address:
    [ 1843.526975] ffff888111e36880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    [ 1843.528479] ffff888111e36900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    [ 1843.530138] >ffff888111e36980: fc fc fc fc fc fc fc fc fc fc fc fc 02 fc fc fc
    [ 1843.531877] ^
    [ 1843.533287] ffff888111e36a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    [ 1843.534874] ffff888111e36a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    [ 1843.536468] ==================================================================

    This is caused by supplying a too short compression value ('lz') in the
    test-case and comparing it to 'lzo' with strncmp() and a length of 3.
    strncmp() read past the 'lz' when looking for the 'o' and thus caused an
    out-of-bounds read.

    Introduce a new check 'btrfs_compress_is_valid_type()' which not only
    checks the user-supplied value against known compression types, but also
    employs checks for too short values.

    Reported-by: Nikolay Borisov <nborisov@suse.com>
    Fixes: 272e5326c783 ("btrfs: prop: fix vanished compression property after failed set")
    CC: stable@vger.kernel.org # 5.1+
    Reviewed-by: Nikolay Borisov <nborisov@suse.com>
    Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
    Reviewed-by: David Sterba <dsterba@suse.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/btrfs/compression.c | 16 ++++++++++++++++
    fs/btrfs/compression.h | 1 +
    fs/btrfs/props.c | 6 +-----
    3 files changed, 18 insertions(+), 5 deletions(-)

    --- a/fs/btrfs/compression.c
    +++ b/fs/btrfs/compression.c
    @@ -42,6 +42,22 @@ const char* btrfs_compress_type2str(enum
    return NULL;
    }

    +bool btrfs_compress_is_valid_type(const char *str, size_t len)
    +{
    + int i;
    +
    + for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) {
    + size_t comp_len = strlen(btrfs_compress_types[i]);
    +
    + if (len < comp_len)
    + continue;
    +
    + if (!strncmp(btrfs_compress_types[i], str, comp_len))
    + return true;
    + }
    + return false;
    +}
    +
    static int btrfs_decompress_bio(struct compressed_bio *cb);

    static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
    --- a/fs/btrfs/compression.h
    +++ b/fs/btrfs/compression.h
    @@ -173,6 +173,7 @@ extern const struct btrfs_compress_op bt
    extern const struct btrfs_compress_op btrfs_zstd_compress;

    const char* btrfs_compress_type2str(enum btrfs_compression_type type);
    +bool btrfs_compress_is_valid_type(const char *str, size_t len);

    int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end);

    --- a/fs/btrfs/props.c
    +++ b/fs/btrfs/props.c
    @@ -257,11 +257,7 @@ static int prop_compression_validate(con
    if (!value)
    return 0;

    - if (!strncmp("lzo", value, 3))
    - return 0;
    - else if (!strncmp("zlib", value, 4))
    - return 0;
    - else if (!strncmp("zstd", value, 4))
    + if (btrfs_compress_is_valid_type(value, len))
    return 0;

    return -EINVAL;

    \
     
     \ /
      Last update: 2019-07-24 22:39    [W:4.309 / U:0.620 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site