From: Qian Cai cai@lca.pw
[ Upstream commit 4982bff1ace1196843f55536fcd4cc119738fe39 ]
In xfs_da3_path_shift() "blk" can be assigned to state->path.blk[-1] if state->path.active is 1 (which is a valid state) when it tries to add an entry to a single dir leaf block and then to shift forward to see if there's a sibling block that would be a better place to put the new entry. This causes a UBSAN warning given negative array indices are undefined behavior in C. In practice the warning is entirely harmless given that "blk" is never dereferenced in this case, but it is still better to fix up the warning and slightly improve the code.
UBSAN: Undefined behaviour in fs/xfs/libxfs/xfs_da_btree.c:1989:14 index -1 is out of range for type 'xfs_da_state_blk_t [5]' Call trace: dump_backtrace+0x0/0x2c8 show_stack+0x20/0x2c dump_stack+0xe8/0x150 __ubsan_handle_out_of_bounds+0xe4/0xfc xfs_da3_path_shift+0x860/0x86c [xfs] xfs_da3_node_lookup_int+0x7c8/0x934 [xfs] xfs_dir2_node_addname+0x2c8/0xcd0 [xfs] xfs_dir_createname+0x348/0x38c [xfs] xfs_create+0x6b0/0x8b4 [xfs] xfs_generic_create+0x12c/0x1f8 [xfs] xfs_vn_mknod+0x3c/0x4c [xfs] xfs_vn_create+0x34/0x44 [xfs] do_last+0xd4c/0x10c8 path_openat+0xbc/0x2f4 do_filp_open+0x74/0xf4 do_sys_openat2+0x98/0x180 __arm64_sys_openat+0xf8/0x170 do_el0_svc+0x170/0x240 el0_sync_handler+0x150/0x250 el0_sync+0x164/0x180
Suggested-by: Christoph Hellwig hch@infradead.org Signed-off-by: Qian Cai cai@lca.pw Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/xfs/libxfs/xfs_da_btree.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c index 8c3eafe280edf..201ce400daa7e 100644 --- a/fs/xfs/libxfs/xfs_da_btree.c +++ b/fs/xfs/libxfs/xfs_da_btree.c @@ -1986,7 +1986,8 @@ xfs_da3_path_shift( ASSERT(path != NULL); ASSERT((path->active > 0) && (path->active < XFS_DA_NODE_MAXDEPTH)); level = (path->active-1) - 1; /* skip bottom layer in path */ - for (blk = &path->blk[level]; level >= 0; blk--, level--) { + for (; level >= 0; level--) { + blk = &path->blk[level]; xfs_da3_node_hdr_from_disk(dp->i_mount, &nodehdr, blk->bp->b_addr);