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author | Christophe Leroy <christophe.leroy@c-s.fr> | 2019-08-21 18:05:55 +0300 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2019-09-09 15:59:14 +0300 |
commit | 3acd48507dc43eeeb0a1fe965b8bad91cab904a7 (patch) | |
tree | 5dd3e0e79f99ed6e28f36dc267ae7c22dbcba542 /fs/btrfs/free-space-cache.c | |
parent | 62fdaa52a3d00a875da771719b6dc537ca79fce1 (diff) | |
download | linux-3acd48507dc43eeeb0a1fe965b8bad91cab904a7.tar.xz |
btrfs: fix allocation of free space cache v1 bitmap pages
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>
Diffstat (limited to 'fs/btrfs/free-space-cache.c')
-rw-r--r-- | fs/btrfs/free-space-cache.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 265dc75f7a7a..ab806d82fe12 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -765,7 +765,8 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode, } else { ASSERT(num_bitmaps); num_bitmaps--; - e->bitmap = kzalloc(PAGE_SIZE, GFP_NOFS); + e->bitmap = kmem_cache_zalloc( + btrfs_free_space_bitmap_cachep, GFP_NOFS); if (!e->bitmap) { kmem_cache_free( btrfs_free_space_cachep, e); @@ -1882,7 +1883,7 @@ static void free_bitmap(struct btrfs_free_space_ctl *ctl, struct btrfs_free_space *bitmap_info) { unlink_free_space(ctl, bitmap_info); - kfree(bitmap_info->bitmap); + kmem_cache_free(btrfs_free_space_bitmap_cachep, bitmap_info->bitmap); kmem_cache_free(btrfs_free_space_cachep, bitmap_info); ctl->total_bitmaps--; ctl->op->recalc_thresholds(ctl); @@ -2136,7 +2137,8 @@ new_bitmap: } /* allocate the bitmap */ - info->bitmap = kzalloc(PAGE_SIZE, GFP_NOFS); + info->bitmap = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep, + GFP_NOFS); spin_lock(&ctl->tree_lock); if (!info->bitmap) { ret = -ENOMEM; @@ -2147,7 +2149,9 @@ new_bitmap: out: if (info) { - kfree(info->bitmap); + if (info->bitmap) + kmem_cache_free(btrfs_free_space_bitmap_cachep, + info->bitmap); kmem_cache_free(btrfs_free_space_cachep, info); } @@ -2811,7 +2815,8 @@ out: if (entry->bytes == 0) { ctl->free_extents--; if (entry->bitmap) { - kfree(entry->bitmap); + kmem_cache_free(btrfs_free_space_bitmap_cachep, + entry->bitmap); ctl->total_bitmaps--; ctl->op->recalc_thresholds(ctl); } @@ -3615,7 +3620,7 @@ again: } if (!map) { - map = kzalloc(PAGE_SIZE, GFP_NOFS); + map = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep, GFP_NOFS); if (!map) { kmem_cache_free(btrfs_free_space_cachep, info); return -ENOMEM; @@ -3644,7 +3649,8 @@ again: if (info) kmem_cache_free(btrfs_free_space_cachep, info); - kfree(map); + if (map) + kmem_cache_free(btrfs_free_space_bitmap_cachep, map); return 0; } |