]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/commit
btrfs: fix allocation of free space cache v1 bitmap pages
authorChristophe Leroy <christophe.leroy@c-s.fr>
Wed, 21 Aug 2019 15:05:55 +0000 (15:05 +0000)
committerKleber Sacilotto de Souza <kleber.souza@canonical.com>
Wed, 16 Oct 2019 09:55:39 +0000 (11:55 +0200)
commita721c8ca2c8cda5b5975ffd6c6d3c6706fa02501
treedab389f6c51b663c6ca8a80f8518e9f0cd5fd38e
parent7bb441bb1b3f8b20b335b57c9d620db993fdc2fe
btrfs: fix allocation of free space cache v1 bitmap pages

BugLink: https://bugs.launchpad.net/bugs/1847155
commit 3acd48507dc43eeeb0a1fe965b8bad91cab904a7 upstream.

Various notifications of type "BUG kmalloc-4096 () : Redzone
overwritten" have been observed recently in various parts of the kernel.
After some time, it has been made a relation with the use of BTRFS
filesystem and with SLUB_DEBUG turned on.

[   22.809700] BUG kmalloc-4096 (Tainted: G        W        ): Redzone overwritten

[   22.810286] INFO: 0xbe1a5921-0xfbfc06cd. First byte 0x0 instead of 0xcc
[   22.810866] INFO: Allocated in __load_free_space_cache+0x588/0x780 [btrfs] age=22 cpu=0 pid=224
[   22.811193]  __slab_alloc.constprop.26+0x44/0x70
[   22.811345]  kmem_cache_alloc_trace+0xf0/0x2ec
[   22.811588]  __load_free_space_cache+0x588/0x780 [btrfs]
[   22.811848]  load_free_space_cache+0xf4/0x1b0 [btrfs]
[   22.812090]  cache_block_group+0x1d0/0x3d0 [btrfs]
[   22.812321]  find_free_extent+0x680/0x12a4 [btrfs]
[   22.812549]  btrfs_reserve_extent+0xec/0x220 [btrfs]
[   22.812785]  btrfs_alloc_tree_block+0x178/0x5f4 [btrfs]
[   22.813032]  __btrfs_cow_block+0x150/0x5d4 [btrfs]
[   22.813262]  btrfs_cow_block+0x194/0x298 [btrfs]
[   22.813484]  commit_cowonly_roots+0x44/0x294 [btrfs]
[   22.813718]  btrfs_commit_transaction+0x63c/0xc0c [btrfs]
[   22.813973]  close_ctree+0xf8/0x2a4 [btrfs]
[   22.814107]  generic_shutdown_super+0x80/0x110
[   22.814250]  kill_anon_super+0x18/0x30
[   22.814437]  btrfs_kill_super+0x18/0x90 [btrfs]
[   22.814590] INFO: Freed in proc_cgroup_show+0xc0/0x248 age=41 cpu=0 pid=83
[   22.814841]  proc_cgroup_show+0xc0/0x248
[   22.814967]  proc_single_show+0x54/0x98
[   22.815086]  seq_read+0x278/0x45c
[   22.815190]  __vfs_read+0x28/0x17c
[   22.815289]  vfs_read+0xa8/0x14c
[   22.815381]  ksys_read+0x50/0x94
[   22.815475]  ret_from_syscall+0x0/0x38

Commit 69d2480456d1 ("btrfs: use copy_page for copying pages instead of
memcpy") changed the way bitmap blocks are copied. But allthough bitmaps
have the size of a page, they were allocated with kzalloc().

Most of the time, kzalloc() allocates aligned blocks of memory, so
copy_page() can be used. But when some debug options like SLAB_DEBUG are
activated, kzalloc() may return unaligned pointer.

On powerpc, memcpy(), copy_page() and other copying functions use
'dcbz' instruction which provides an entire zeroed cacheline to avoid
memory read when the intention is to overwrite a full line. Functions
like memcpy() are writen to care about partial cachelines at the start
and end of the destination, but copy_page() assumes it gets pages. As
pages are naturally cache aligned, copy_page() doesn't care about
partial lines. This means that when copy_page() is called with a
misaligned pointer, a few leading bytes are zeroed.

To fix it, allocate bitmaps through kmem_cache instead of using kzalloc()
The cache pool is created with PAGE_SIZE alignment constraint.

Reported-by: Erhard F. <erhard_f@mailbox.org>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204371
Fixes: 69d2480456d1 ("btrfs: use copy_page for copying pages instead of memcpy")
Cc: stable@vger.kernel.org # 4.19+
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: David Sterba <dsterba@suse.com>
[ rename to btrfs_free_space_bitmap ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
fs/btrfs/ctree.h
fs/btrfs/free-space-cache.c
fs/btrfs/inode.c