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It does not compare the number of levels traversed with the B-tree superblock's max_depth field. A crafted directory B-tree can therefore make an empty interior root point its overflow field back to itself. Directory iteration remains in befs_btree_seekleaf() indefinitely. The same unbounded descent exists in befs_btree_find(). Track the descent depth in both paths and reject trees that exceed their declared maximum depth. Also apply a 64-level absolute limit so a corrupted max_depth value cannot itself make the bound ineffective. A valid B-tree in a 64-bit address space cannot require more than 64 interior levels. This is separate from validation of the packed key layout inside each node; the looping image uses a structurally valid empty node and malformed graph connectivity. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Sangho Lee --- fs/befs/btree.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/fs/befs/btree.c b/fs/befs/btree.c index aa24f1dac..f27e8c94e 100644 --- a/fs/befs/btree.c +++ b/fs/befs/btree.c @@ -87,6 +87,8 @@ struct befs_btree_node { /* local constants */ static const befs_off_t BEFS_BT_INVAL =3D 0xffffffffffffffffULL; =20 +#define BEFS_BTREE_MAX_DEPTH 64 + /* local functions */ static int befs_btree_seekleaf(struct super_block *sb, const befs_data_str= eam *ds, befs_btree_super * bt_super, @@ -248,6 +250,7 @@ befs_btree_find(struct super_block *sb, const befs_data= _stream *ds, struct befs_btree_node *this_node; befs_btree_super bt_super; befs_off_t node_off; + u32 depth =3D 0; int res; =20 befs_debug(sb, "---> %s Key: %s", __func__, key); @@ -276,6 +279,12 @@ befs_btree_find(struct super_block *sb, const befs_dat= a_stream *ds, } =20 while (!befs_leafnode(this_node)) { + if (++depth > bt_super.max_depth || + depth > BEFS_BTREE_MAX_DEPTH) { + befs_error(sb, "B-tree depth exceeds limit"); + goto error_alloc; + } + res =3D befs_find_key(sb, this_node, key, &node_off); /* if no key set, try the overflow node */ if (res =3D=3D BEFS_BT_OVERFLOW) @@ -543,6 +552,7 @@ befs_btree_seekleaf(struct super_block *sb, const befs_= data_stream *ds, struct befs_btree_node *this_node, befs_off_t * node_off) { + u32 depth =3D 0; =20 befs_debug(sb, "---> %s", __func__); =20 @@ -559,6 +569,11 @@ befs_btree_seekleaf(struct super_block *sb, const befs= _data_stream *ds, } =20 while (!befs_leafnode(this_node)) { + if (++depth > bt_super->max_depth || + depth > BEFS_BTREE_MAX_DEPTH) { + befs_error(sb, "B-tree depth exceeds limit"); + goto error; + } =20 if (this_node->head.all_key_count =3D=3D 0) { befs_debug(sb, "%s encountered " --=20 2.43.0