| Message ID | 20191211050004.18414-2-wqu@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: fixes for relocation to avoid KASAN reports | expand |
On 12/11/19 12:00 AM, Qu Wenruo wrote: > [BUG] > When running a workload with balance start/cancel, snapshot creation and > deletion, and fsstress, we can get the following KASAN report: > > ================================================================== > BUG: KASAN: use-after-free in should_ignore_root+0x54/0xb0 [btrfs] > Read of size 8 at addr ffff888146e340f0 by task btrfs/1216 > > CPU: 6 PID: 1216 Comm: btrfs Tainted: G O 5.5.0-rc1-custom+ #40 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 > Call Trace: > dump_stack+0xc2/0x11a > print_address_description.constprop.0+0x20/0x210 > __kasan_report.cold+0x1b/0x41 > kasan_report+0x12/0x20 > check_memory_region+0x13c/0x1b0 > __asan_loadN+0xf/0x20 > should_ignore_root+0x54/0xb0 [btrfs] > build_backref_tree+0x11af/0x2280 [btrfs] > relocate_tree_blocks+0x391/0xb80 [btrfs] > relocate_block_group+0x3e5/0xa00 [btrfs] > btrfs_relocate_block_group+0x240/0x4d0 [btrfs] > btrfs_relocate_chunk+0x53/0xf0 [btrfs] > btrfs_balance+0xc91/0x1840 [btrfs] > btrfs_ioctl_balance+0x416/0x4e0 [btrfs] > btrfs_ioctl+0x8af/0x3e60 [btrfs] > do_vfs_ioctl+0x831/0xb10 > ksys_ioctl+0x67/0x90 > __x64_sys_ioctl+0x43/0x50 > do_syscall_64+0x79/0xe0 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > [CAUSE] > When should_ignore_root() accessing root->reloc_root, the reloc_root can > be being dropped, thus root->reloc_root can be unreliable. > > [FIX] > Check DEAD_RELOC_ROOT bit before accessing root->reloc_root. > > Furthermore in the context of should_ignore_root(), if the root has > already gone through tree merge, we don't need to trace that root > anymore. > Thus we need to return 1, for root with dead reloc root. > > Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org> > Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") > Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Thanks, Josef
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index d897a8e5e430..bb41b981e493 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -525,6 +525,10 @@ static int should_ignore_root(struct btrfs_root *root) if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state)) return 0; + /* This root has been merged with its reloc tree, so we can ignore it */ + if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state)) + return 1; + reloc_root = root->reloc_root; if (!reloc_root) return 0;
[BUG] When running a workload with balance start/cancel, snapshot creation and deletion, and fsstress, we can get the following KASAN report: ================================================================== BUG: KASAN: use-after-free in should_ignore_root+0x54/0xb0 [btrfs] Read of size 8 at addr ffff888146e340f0 by task btrfs/1216 CPU: 6 PID: 1216 Comm: btrfs Tainted: G O 5.5.0-rc1-custom+ #40 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: dump_stack+0xc2/0x11a print_address_description.constprop.0+0x20/0x210 __kasan_report.cold+0x1b/0x41 kasan_report+0x12/0x20 check_memory_region+0x13c/0x1b0 __asan_loadN+0xf/0x20 should_ignore_root+0x54/0xb0 [btrfs] build_backref_tree+0x11af/0x2280 [btrfs] relocate_tree_blocks+0x391/0xb80 [btrfs] relocate_block_group+0x3e5/0xa00 [btrfs] btrfs_relocate_block_group+0x240/0x4d0 [btrfs] btrfs_relocate_chunk+0x53/0xf0 [btrfs] btrfs_balance+0xc91/0x1840 [btrfs] btrfs_ioctl_balance+0x416/0x4e0 [btrfs] btrfs_ioctl+0x8af/0x3e60 [btrfs] do_vfs_ioctl+0x831/0xb10 ksys_ioctl+0x67/0x90 __x64_sys_ioctl+0x43/0x50 do_syscall_64+0x79/0xe0 entry_SYSCALL_64_after_hwframe+0x49/0xbe [CAUSE] When should_ignore_root() accessing root->reloc_root, the reloc_root can be being dropped, thus root->reloc_root can be unreliable. [FIX] Check DEAD_RELOC_ROOT bit before accessing root->reloc_root. Furthermore in the context of should_ignore_root(), if the root has already gone through tree merge, we don't need to trace that root anymore. Thus we need to return 1, for root with dead reloc root. Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org> Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/relocation.c | 4 ++++ 1 file changed, 4 insertions(+)