The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c57dd1f2f6a7cd1bb61802344f59ccdc5278c983 Mon Sep 17 00:00:00 2001

From: Qu Wenruo wqu@suse.com Date: Fri, 31 Jul 2020 19:29:11 +0800 Subject: [PATCH] btrfs: trim: fix underflow in trim length to prevent access beyond device boundary

[BUG] The following script can lead to tons of beyond device boundary access:

mkfs.btrfs -f $dev -b 10G mount $dev $mnt trimfs $mnt btrfs filesystem resize 1:-1G $mnt trimfs $mnt

[CAUSE] Since commit 929be17a9b49 ("btrfs: Switch btrfs_trim_free_extents to find_first_clear_extent_bit"), we try to avoid trimming ranges that's already trimmed.

So we check device->alloc_state by finding the first range which doesn't have CHUNK_TRIMMED and CHUNK_ALLOCATED not set.

But if we shrunk the device, that bits are not cleared, thus we could easily got a range starts beyond the shrunk device size.

This results the returned @start and @end are all beyond device size, then we call "end = min(end, device->total_bytes -1);" making @end smaller than device size.

Then finally we goes "len = end - start + 1", totally underflow the result, and lead to the beyond-device-boundary access.

[FIX] This patch will fix the problem in two ways:

- Clear CHUNK_TRIMMED | CHUNK_ALLOCATED bits when shrinking device This is the root fix

- Add extra safety check when trimming free device extents We check and warn if the returned range is already beyond current device.

Link: https://github.com/kdave/btrfs-progs/issues/282 Fixes: 929be17a9b49 ("btrfs: Switch btrfs_trim_free_extents to find_first_clear_extent_bit") CC: stable@vger.kernel.org # 5.4+ Signed-off-by: Qu Wenruo wqu@suse.com Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com

diff --git a/fs/btrfs/extent-io-tree.h b/fs/btrfs/extent-io-tree.h index f39d47a2d01a..219a09a2b734 100644 --- a/fs/btrfs/extent-io-tree.h +++ b/fs/btrfs/extent-io-tree.h @@ -34,6 +34,8 @@ struct io_failure_record; */ #define CHUNK_ALLOCATED EXTENT_DIRTY #define CHUNK_TRIMMED EXTENT_DEFRAG +#define CHUNK_STATE_MASK (CHUNK_ALLOCATED | \ + CHUNK_TRIMMED)

enum { IO_TREE_FS_PINNED_EXTENTS, diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 61ede335f6c3..de6fe176fdfb 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -33,6 +33,7 @@ #include "delalloc-space.h" #include "block-group.h" #include "discard.h" +#include "rcu-string.h"

#undef SCRAMBLE_DELAYED_REFS

@@ -5668,6 +5669,19 @@ static int btrfs_trim_free_extents(struct btrfs_device *device, u64 *trimmed) &start, &end, CHUNK_TRIMMED | CHUNK_ALLOCATED);

+ /* Check if there are any CHUNK_* bits left */ + if (start > device->total_bytes) { + WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG)); + btrfs_warn_in_rcu(fs_info, +"ignoring attempt to trim beyond device size: offset %llu length %llu device %s device size %llu", + start, end - start + 1, + rcu_str_deref(device->name), + device->total_bytes); + mutex_unlock(&fs_info->chunk_mutex); + ret = 0; + break; + } + /* Ensure we skip the reserved area in the first 1M */ start = max_t(u64, start, SZ_1M);

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index d7670e2a9f39..ee96c5869f57 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4720,6 +4720,10 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) }

mutex_lock(&fs_info->chunk_mutex); + /* Clear all state bits beyond the shrunk device size */ + clear_extent_bits(&device->alloc_state, new_size, (u64)-1, + CHUNK_STATE_MASK); + btrfs_device_set_disk_total_bytes(device, new_size); if (list_empty(&device->post_commit_list)) list_add_tail(&device->post_commit_list,