Running "btrfsck --repair /dev/sdd2" crashed as it can happen in
(corrupted) file systems, that slot > nritems:
> (gdb) bt full
> #0 0x00007ffff7020e71 in __memmove_sse2_unaligned_erms () from
> /lib/x86_64-linux-gnu/libc.so.6
> #1 0x0000000000438764 in btrfs_del_ptr (trans=<optimized out>,
> root=0x6e4fe0, path=0x1d17880, level=0, slot=7)
> at ctree.c:2611
> parent = 0xcd96980
> nritems = <optimized out>
> __func__ = "btrfs_del_ptr"
> #2 0x0000000000421b15 in repair_btree (corrupt_blocks=<optimized out>,
> root=<optimized out>) at cmds-check.c:3539
> key = {objectid = 77990592512, type = 168 '\250', offset = 16384}
> trans = 0x8f48c0
> path = 0x1d17880
> level = 0
> #3 check_fs_root (wc=<optimized out>, root_cache=<optimized out>,
> root=<optimized out>) at cmds-check.c:3703
> corrupt = 0x1d17880
> corrupt_blocks = {root = {rb_node = 0x6e80c60}}
> path = {nodes = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, slots = {0,
> 0, 0, 0, 0, 0, 0, 0}, locks = {0, 0,
> 0, 0, 0, 0, 0, 0}, reada = 0, lowest_level = 0, search_for_split
> = 0, skip_check_block = 0}
> nrefs = {bytenr = {271663104, 271646720, 560021504, 0, 0, 0, 0, 0},
> refs = {1, 1, 1, 0, 0, 0, 0, 0}}
> wret = 215575372
> root_node = {cache = {rb_node = {__rb_parent_color = 0, rb_right =
> 0x0, rb_left = 0x0}, objectid = 0,
> start = 0, size = 0}, root_cache = {root = {rb_node = 0x0}},
> inode_cache = {root = {
> rb_node = 0x781c80}}, current = 0x819530, refs = 0}
> status = 215575372
> rec = 0x1
> #4 check_fs_roots (root_cache=0xcd96b6d, root=<optimized out>) at
> cmds-check.c:3809
> path = {nodes = {0x6eed90, 0x6a2f40, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
> slots = {18, 2, 0, 0, 0, 0, 0, 0},
> locks = {0, 0, 0, 0, 0, 0, 0, 0}, reada = 0, lowest_level = 0,
> search_for_split = 0,
> skip_check_block = 0}
> key = {objectid = 323, type = 132 '\204', offset =
> 18446744073709551615}
> wc = {shared = {root = {rb_node = 0x0}}, nodes = {0x0, 0x0,
> 0x7fffffffe428, 0x0, 0x0, 0x0, 0x0, 0x0},
> active_node = 2, root_level = 2}
> leaf = 0x6e4fe0
> tmp_root = 0x6e4fe0
> #5 0x00000000004287c3 in cmd_check (argc=215575372, argv=0x1d17880) at
> cmds-check.c:11521
> root_cache = {root = {rb_node = 0x98c2940}}
> info = 0x6927b0
> bytenr = 6891440
> tree_root_bytenr = 0
> uuidbuf = "f65ff1a1-76ef-456e-beb5-c6c3841e7534"
> num = 215575372
> readonly = 218080104
> qgroups_repaired = 0
> #6 0x000000000040a41f in main (argc=3, argv=0x7fffffffebe8) at btrfs.c:243
> cmd = 0x689868
> bname = <optimized out>
> ret = <optimized out>
in that case the count of remaining items (nritems - slot - 1) gets
negative. That is then casted to (unsigned long len), which leads to the
observed crash.
Change the tests before the move to handle only the non-corrupted case,
were slow < nritems.
This does not fix the corruption, but allows btrfsck to finish without
crashing.
Signed-off-by: Philipp Hahn <h...@univention.de>
---
ctree.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/ctree.c b/ctree.c
index 02c7180..798bde9 100644
--- a/ctree.c
+++ b/ctree.c
@@ -1487,7 +1487,8 @@ static int insert_ptr(struct btrfs_trans_handle *trans,
struct btrfs_root
BUG();
if (nritems == BTRFS_NODEPTRS_PER_BLOCK(root))
BUG();
- if (slot != nritems) {
+ if (slot < nritems) {
+ /* shift the items */
memmove_extent_buffer(lower,
btrfs_node_key_ptr_offset(slot + 1),
btrfs_node_key_ptr_offset(slot),
@@ -2249,7 +2250,7 @@ split:
nritems = btrfs_header_nritems(leaf);
- if (slot != nritems) {
+ if (slot < nritems) {
/* shift the items */
memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + 1),
btrfs_item_nr_offset(slot),
@@ -2500,7 +2501,7 @@ int btrfs_insert_empty_items(struct btrfs_trans_handle
*trans,
slot = path->slots[0];
BUG_ON(slot < 0);
- if (slot != nritems) {
+ if (slot < nritems) {
unsigned int old_data = btrfs_item_end_nr(leaf, slot);
if (old_data < data_end) {
@@ -2603,7 +2604,8 @@ int btrfs_del_ptr(struct btrfs_root *root, struct
btrfs_path *path,
int ret = 0;
nritems = btrfs_header_nritems(parent);
- if (slot != nritems -1) {
+ if (slot < nritems -1) {
+ /* shift the items */
memmove_extent_buffer(parent,
btrfs_node_key_ptr_offset(slot),
btrfs_node_key_ptr_offset(slot + 1),
--
2.11.0
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