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A malformed ROOT_BACKREF can therefore make the length underflow or exceed the fixed ioctl buffer. Validate that the item is large enough for struct btrfs_root_ref, that the on-disk name_len fits inside the remaining payload, and that the copied name does not exceed BTRFS_VOL_NAME_MAX. If any of those checks fail, return -EUCLEAN instead of copying from corrupted metadata. After validation, copy only name_len bytes and terminate the result explicitly. Sanitizer validation reported: BUG: KASAN: slab-out-of-bounds in read_extent_buffer() Write of size 505 at addr ffff88810936d608 Call trace: dump_stack_lvl() (?:?) print_address_description() (mm/kasan/report.c:373) read_extent_buffer() (?:?) print_report() (?:?) __virt_addr_valid() (?:?) srso_alias_return_thunk() (arch/x86/include/asm/nospec-branch.h:375) kasan_addr_to_slab() (mm/kasan/common.c:45) kasan_report() (?:?) kasan_check_range() (?:?) __asan_memcpy() (mm/kasan/shadow.c:103) btrfs_ioctl_get_subvol_info() (fs/btrfs/ioctl.c:2034) btrfs_get_32() (fs/btrfs/ioctl.c:?) btrfs_set_16() (fs/btrfs/ioctl.c:?) btrfs_test_get_subvol_info_name_oob() (fs/btrfs/ioctl.c:?) btrfs_run_sanity_tests() (fs/btrfs/ioctl.c:?) init_btrfs_fs() (fs/btrfs/super.c:2690) do_one_initcall() (init/main.c:1382) __kasan_kmalloc() (?:?) rcu_is_watching() (?:?) do_initcalls() (init/main.c:1457) kernel_init_freeable() (init/main.c:1674) kernel_init() (init/main.c:1584) ret_from_fork() (?:?) __switch_to() (?:?) ret_from_fork_asm() (?:?) kasan_save_stack() (mm/kasan/common.c:52) kasan_save_track() (mm/kasan/common.c:74) Signed-off-by: Zhang Cen --- diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index a39460bf68a7..0647e672464a 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1956,7 +1956,8 @@ static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp) struct btrfs_root_ref *rref; struct extent_buffer *leaf; unsigned long item_off; - unsigned long item_len; + u32 item_size; + u16 name_len; int slot; int ret = 0; @@ -2034,14 +2035,26 @@ static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp) subvol_info->parent_id = key.offset; rref = btrfs_item_ptr(leaf, slot, struct btrfs_root_ref); + item_size = btrfs_item_size(leaf, slot); + if (item_size < sizeof(*rref)) { + ret = -EUCLEAN; + goto out; + } + + name_len = btrfs_root_ref_name_len(leaf, rref); + if (name_len > item_size - sizeof(*rref) || + name_len > BTRFS_VOL_NAME_MAX) { + ret = -EUCLEAN; + goto out; + } + subvol_info->dirid = btrfs_root_ref_dirid(leaf, rref); - item_off = btrfs_item_ptr_offset(leaf, slot) - + sizeof(struct btrfs_root_ref); - item_len = btrfs_item_size(leaf, slot) - - sizeof(struct btrfs_root_ref); + item_off = btrfs_item_ptr_offset(leaf, slot) + + sizeof(*rref); read_extent_buffer(leaf, subvol_info->name, - item_off, item_len); + item_off, name_len); + subvol_info->name[name_len] = '\0'; } else { ret = -ENOENT; goto out;