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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 Commit69d2480456
("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:69d2480456
("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>
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parent
62fdaa52a3
commit
3acd48507d
3 changed files with 22 additions and 7 deletions
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@ -43,6 +43,7 @@ extern struct kmem_cache *btrfs_trans_handle_cachep;
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extern struct kmem_cache *btrfs_bit_radix_cachep;
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extern struct kmem_cache *btrfs_path_cachep;
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extern struct kmem_cache *btrfs_free_space_cachep;
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extern struct kmem_cache *btrfs_free_space_bitmap_cachep;
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struct btrfs_ordered_sum;
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struct btrfs_ref;
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@ -765,7 +765,8 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
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} else {
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ASSERT(num_bitmaps);
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num_bitmaps--;
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e->bitmap = kzalloc(PAGE_SIZE, GFP_NOFS);
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e->bitmap = kmem_cache_zalloc(
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btrfs_free_space_bitmap_cachep, GFP_NOFS);
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if (!e->bitmap) {
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kmem_cache_free(
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btrfs_free_space_cachep, e);
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@ -1882,7 +1883,7 @@ static void free_bitmap(struct btrfs_free_space_ctl *ctl,
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struct btrfs_free_space *bitmap_info)
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{
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unlink_free_space(ctl, bitmap_info);
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kfree(bitmap_info->bitmap);
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kmem_cache_free(btrfs_free_space_bitmap_cachep, bitmap_info->bitmap);
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kmem_cache_free(btrfs_free_space_cachep, bitmap_info);
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ctl->total_bitmaps--;
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ctl->op->recalc_thresholds(ctl);
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@ -2136,7 +2137,8 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
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}
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/* allocate the bitmap */
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info->bitmap = kzalloc(PAGE_SIZE, GFP_NOFS);
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info->bitmap = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep,
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GFP_NOFS);
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spin_lock(&ctl->tree_lock);
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if (!info->bitmap) {
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ret = -ENOMEM;
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@ -2147,7 +2149,9 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
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out:
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if (info) {
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kfree(info->bitmap);
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if (info->bitmap)
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kmem_cache_free(btrfs_free_space_bitmap_cachep,
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info->bitmap);
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kmem_cache_free(btrfs_free_space_cachep, info);
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}
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@ -2811,7 +2815,8 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
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if (entry->bytes == 0) {
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ctl->free_extents--;
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if (entry->bitmap) {
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kfree(entry->bitmap);
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kmem_cache_free(btrfs_free_space_bitmap_cachep,
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entry->bitmap);
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ctl->total_bitmaps--;
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ctl->op->recalc_thresholds(ctl);
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}
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@ -3615,7 +3620,7 @@ int test_add_free_space_entry(struct btrfs_block_group_cache *cache,
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}
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if (!map) {
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map = kzalloc(PAGE_SIZE, GFP_NOFS);
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map = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep, GFP_NOFS);
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if (!map) {
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kmem_cache_free(btrfs_free_space_cachep, info);
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return -ENOMEM;
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@ -3644,7 +3649,8 @@ int test_add_free_space_entry(struct btrfs_block_group_cache *cache,
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if (info)
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kmem_cache_free(btrfs_free_space_cachep, info);
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kfree(map);
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if (map)
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kmem_cache_free(btrfs_free_space_bitmap_cachep, map);
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return 0;
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}
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@ -74,6 +74,7 @@ static struct kmem_cache *btrfs_inode_cachep;
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struct kmem_cache *btrfs_trans_handle_cachep;
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struct kmem_cache *btrfs_path_cachep;
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struct kmem_cache *btrfs_free_space_cachep;
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struct kmem_cache *btrfs_free_space_bitmap_cachep;
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static int btrfs_setsize(struct inode *inode, struct iattr *attr);
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static int btrfs_truncate(struct inode *inode, bool skip_writeback);
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@ -9409,6 +9410,7 @@ void __cold btrfs_destroy_cachep(void)
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kmem_cache_destroy(btrfs_trans_handle_cachep);
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kmem_cache_destroy(btrfs_path_cachep);
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kmem_cache_destroy(btrfs_free_space_cachep);
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kmem_cache_destroy(btrfs_free_space_bitmap_cachep);
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}
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int __init btrfs_init_cachep(void)
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@ -9438,6 +9440,12 @@ int __init btrfs_init_cachep(void)
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if (!btrfs_free_space_cachep)
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goto fail;
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btrfs_free_space_bitmap_cachep = kmem_cache_create("btrfs_free_space_bitmap",
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PAGE_SIZE, PAGE_SIZE,
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SLAB_RED_ZONE, NULL);
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if (!btrfs_free_space_bitmap_cachep)
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goto fail;
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return 0;
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fail:
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btrfs_destroy_cachep();
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