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btrfs: Check name_len with boundary in verify dir_item

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Originally, verify_dir_item verifies name_len of dir_item with fixed
values but not item boundary.
If corrupted name_len was not bigger than the fixed value, for example
255, the function will think the dir_item is fine. And then reading
beyond boundary will cause crash.

Example:
	1. Corrupt one dir_item name_len to be 255.
        2. Run 'ls -lar /mnt/test/ > /dev/null'
dmesg:
[   48.451449] BTRFS info (device vdb1): disk space caching is enabled
[   48.451453] BTRFS info (device vdb1): has skinny extents
[   48.489420] general protection fault: 0000 [#1] SMP
[   48.489571] Modules linked in: ext4 jbd2 mbcache btrfs xor raid6_pq
[   48.489716] CPU: 1 PID: 2710 Comm: ls Not tainted 4.10.0-rc1 #5
[   48.489853] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-20170228_101828-anatol 04/01/2014
[   48.490008] task: ffff880035df1bc0 task.stack: ffffc90004800000
[   48.490008] RIP: 0010:read_extent_buffer+0xd2/0x190 [btrfs]
[   48.490008] RSP: 0018:ffffc90004803d98 EFLAGS: 00010202
[   48.490008] RAX: 000000000000001b RBX: 000000000000001b RCX: 0000000000000000
[   48.490008] RDX: ffff880079dbf36c RSI: 0005080000000000 RDI: ffff880079dbf368
[   48.490008] RBP: ffffc90004803dc8 R08: ffff880078e8cc48 R09: ffff880000000000
[   48.490008] R10: 0000160000000000 R11: 0000000000001000 R12: ffff880079dbf288
[   48.490008] R13: ffff880078e8ca88 R14: 0000000000000003 R15: ffffc90004803e20
[   48.490008] FS:  00007fef50c60800(0000) GS:ffff88007d400000(0000) knlGS:0000000000000000
[   48.490008] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   48.490008] CR2: 000055f335ac2ff8 CR3: 000000007356d000 CR4: 00000000001406e0
[   48.490008] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   48.490008] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   48.490008] Call Trace:
[   48.490008]  btrfs_real_readdir+0x3b7/0x4a0 [btrfs]
[   48.490008]  iterate_dir+0x181/0x1b0
[   48.490008]  SyS_getdents+0xa7/0x150
[   48.490008]  ? fillonedir+0x150/0x150
[   48.490008]  entry_SYSCALL_64_fastpath+0x18/0xad
[   48.490008] RIP: 0033:0x7fef5032546b
[   48.490008] RSP: 002b:00007ffeafcdb830 EFLAGS: 00000206 ORIG_RAX: 000000000000004e
[   48.490008] RAX: ffffffffffffffda RBX: 00007fef5061db38 RCX: 00007fef5032546b
[   48.490008] RDX: 0000000000008000 RSI: 000055f335abaff0 RDI: 0000000000000003
[   48.490008] RBP: 00007fef5061dae0 R08: 00007fef5061db48 R09: 0000000000000000
[   48.490008] R10: 000055f335abafc0 R11: 0000000000000206 R12: 00007fef5061db38
[   48.490008] R13: 0000000000008040 R14: 00007fef5061db38 R15: 000000000000270e
[   48.490008] RIP: read_extent_buffer+0xd2/0x190 [btrfs] RSP: ffffc90004803d98
[   48.499455] ---[ end trace 321920d8e8339505 ]---

Fix it by adding a parameter @slot and check name_len with item boundary
by calling btrfs_is_name_len_valid.

Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
rev
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Su Yue 2017-06-06 17:57:01 +08:00 committed by David Sterba
parent 19c6dcbfa7
commit e79a33270d
5 changed files with 14 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/btrfs/ctree.h
View File

@ -3036,7 +3036,7 @@ struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
const char *name, u16 name_len,
int mod);
int verify_dir_item(struct btrfs_fs_info *fs_info,
struct extent_buffer *leaf,
struct extent_buffer *leaf, int slot,
struct btrfs_dir_item *dir_item);
struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_fs_info *fs_info,
struct btrfs_path *path,

10
fs/btrfs/dir-item.c
View File

@ -395,7 +395,7 @@ struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_fs_info *fs_info,
leaf = path->nodes[0];
dir_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item);
if (verify_dir_item(fs_info, leaf, dir_item))
if (verify_dir_item(fs_info, leaf, path->slots[0], dir_item))
return NULL;
total_len = btrfs_item_size_nr(leaf, path->slots[0]);
@ -453,9 +453,11 @@ int btrfs_delete_one_dir_name(struct btrfs_trans_handle *trans,
int verify_dir_item(struct btrfs_fs_info *fs_info,
struct extent_buffer *leaf,
int slot,
struct btrfs_dir_item *dir_item)
{
u16 namelen = BTRFS_NAME_LEN;
int ret;
u8 type = btrfs_dir_type(leaf, dir_item);
if (type >= BTRFS_FT_MAX) {
@ -472,6 +474,12 @@ int verify_dir_item(struct btrfs_fs_info *fs_info,
return 1;
}
namelen = btrfs_dir_name_len(leaf, dir_item);
ret = btrfs_is_name_len_valid(leaf, slot,
(unsigned long)(dir_item + 1), namelen);
if (!ret)
return 1;
/* BTRFS_MAX_XATTR_SIZE is the same for all dir items */
if ((btrfs_dir_data_len(leaf, dir_item) +
btrfs_dir_name_len(leaf, dir_item)) >

2
fs/btrfs/inode.c
View File

@ -5934,7 +5934,7 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
ctx->pos = found_key.offset;
di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
if (verify_dir_item(fs_info, leaf, di))
if (verify_dir_item(fs_info, leaf, slot, di))
goto next;
name_len = btrfs_dir_name_len(leaf, di);

4
fs/btrfs/tree-log.c
View File

@ -1841,7 +1841,7 @@ static noinline int replay_one_dir_item(struct btrfs_trans_handle *trans,
ptr_end = ptr + item_size;
while (ptr < ptr_end) {
di = (struct btrfs_dir_item *)ptr;
if (verify_dir_item(fs_info, eb, di))
if (verify_dir_item(fs_info, eb, slot, di))
return -EIO;
name_len = btrfs_dir_name_len(eb, di);
ret = replay_one_name(trans, root, path, eb, di, key);
@ -2017,7 +2017,7 @@ again:
ptr_end = ptr + item_size;
while (ptr < ptr_end) {
di = (struct btrfs_dir_item *)ptr;
if (verify_dir_item(fs_info, eb, di)) {
if (verify_dir_item(fs_info, eb, slot, di)) {
ret = -EIO;
goto out;
}

2
fs/btrfs/xattr.c
View File

@ -336,7 +336,7 @@ ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
u32 this_len = sizeof(*di) + name_len + data_len;
unsigned long name_ptr = (unsigned long)(di + 1);
if (verify_dir_item(fs_info, leaf, di)) {
if (verify_dir_item(fs_info, leaf, slot, di)) {
ret = -EIO;
goto err;
}