diff mbox series

ext4: fix use-after-free in ext4_xattr_set_entry

Message ID 20220602114651.3244889-1-libaokun1@huawei.com
State Superseded
Headers show
Series ext4: fix use-after-free in ext4_xattr_set_entry | expand

Commit Message

Baokun Li June 2, 2022, 11:46 a.m. UTC 
Hulk Robot reported a issue:
==================================================================
BUG: KASAN: use-after-free in ext4_xattr_set_entry+0x18ab/0x3500
Write of size 4105 at addr ffff8881675ef5f4 by task syz-executor.0/7092

CPU: 1 PID: 7092 Comm: syz-executor.0 Not tainted 4.19.90-dirty #17
Call Trace:
[...]
 memcpy+0x34/0x50 mm/kasan/kasan.c:303
 ext4_xattr_set_entry+0x18ab/0x3500 fs/ext4/xattr.c:1747
 ext4_xattr_ibody_inline_set+0x86/0x2a0 fs/ext4/xattr.c:2205
 ext4_xattr_set_handle+0x940/0x1300 fs/ext4/xattr.c:2386
 ext4_xattr_set+0x1da/0x300 fs/ext4/xattr.c:2498
 __vfs_setxattr+0x112/0x170 fs/xattr.c:149
 __vfs_setxattr_noperm+0x11b/0x2a0 fs/xattr.c:180
 __vfs_setxattr_locked+0x17b/0x250 fs/xattr.c:238
 vfs_setxattr+0xed/0x270 fs/xattr.c:255
 setxattr+0x235/0x330 fs/xattr.c:520
 path_setxattr+0x176/0x190 fs/xattr.c:539
 __do_sys_lsetxattr fs/xattr.c:561 [inline]
 __se_sys_lsetxattr fs/xattr.c:557 [inline]
 __x64_sys_lsetxattr+0xc2/0x160 fs/xattr.c:557
 do_syscall_64+0xdf/0x530 arch/x86/entry/common.c:298
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x459fe9
RSP: 002b:00007fa5e54b4c08 EFLAGS: 00000246 ORIG_RAX: 00000000000000bd
RAX: ffffffffffffffda RBX: 000000000051bf60 RCX: 0000000000459fe9
RDX: 00000000200003c0 RSI: 0000000020000180 RDI: 0000000020000140
RBP: 000000000051bf60 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000001009 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc73c93fc0 R14: 000000000051bf60 R15: 00007fa5e54b4d80
[...]
==================================================================

Above issue may happen as follows:
-------------------------------------
ext4_xattr_set
  ext4_xattr_set_handle
    ext4_xattr_ibody_find
      >> s->end < s->base
      >> no EXT4_STATE_XATTR
      >> xattr_check_inode is not executed
    ext4_xattr_ibody_set
      ext4_xattr_set_entry
       >> size_t min_offs = s->end - s->base
       >> UAF in memcpy

we can easily reproduce this problem with the following commands:
    mkfs.ext4 -F /dev/sda
    mount -o debug_want_extra_isize=128 /dev/sda /mnt
    touch /mnt/file
    setfattr -n user.cat -v `seq -s z 4096|tr -d '[:digit:]'` /mnt/file

In ext4_xattr_ibody_find, we have the following assignment logic:
  header = IHDR(inode, raw_inode)
         = raw_inode + EXT4_GOOD_OLD_INODE_SIZE + i_extra_isize
  is->s.base = IFIRST(header)
             = header + sizeof(struct ext4_xattr_ibody_header)
  is->s.end = raw_inode + s_inode_size

Obviously, when the inode does not have EXT4_status_XATTR and its
i_extra_isize is large, is->s.end may be larger than is->s.base.
In this case, the above issue may be triggered.

   EXT4_GOOD_OLD_INODE_SIZE  extra_isize  header   entry   pad   data
|---------------------------|------------|------|---------|---|--------|

As shown above, when adding an xattr to an inode, we must ensure that the
inode_size is not less than EXT4_GOOD_OLD_INODE_SIZE + extra_isize + pad.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
 fs/ext4/inline.c | 3 +++
 fs/ext4/inode.c  | 3 +--
 fs/ext4/xattr.c  | 6 ++++--
 fs/ext4/xattr.h  | 6 ++++++
 4 files changed, 14 insertions(+), 4 deletions(-)

Comments

Jan Kara June 14, 2022, 9:54 a.m. UTC | #1 
On Thu 02-06-22 19:46:51, Baokun Li wrote:
> Hulk Robot reported a issue:
> ==================================================================
> BUG: KASAN: use-after-free in ext4_xattr_set_entry+0x18ab/0x3500
> Write of size 4105 at addr ffff8881675ef5f4 by task syz-executor.0/7092
> 
> CPU: 1 PID: 7092 Comm: syz-executor.0 Not tainted 4.19.90-dirty #17
> Call Trace:
> [...]
>  memcpy+0x34/0x50 mm/kasan/kasan.c:303
>  ext4_xattr_set_entry+0x18ab/0x3500 fs/ext4/xattr.c:1747
>  ext4_xattr_ibody_inline_set+0x86/0x2a0 fs/ext4/xattr.c:2205
>  ext4_xattr_set_handle+0x940/0x1300 fs/ext4/xattr.c:2386
>  ext4_xattr_set+0x1da/0x300 fs/ext4/xattr.c:2498
>  __vfs_setxattr+0x112/0x170 fs/xattr.c:149
>  __vfs_setxattr_noperm+0x11b/0x2a0 fs/xattr.c:180
>  __vfs_setxattr_locked+0x17b/0x250 fs/xattr.c:238
>  vfs_setxattr+0xed/0x270 fs/xattr.c:255
>  setxattr+0x235/0x330 fs/xattr.c:520
>  path_setxattr+0x176/0x190 fs/xattr.c:539
>  __do_sys_lsetxattr fs/xattr.c:561 [inline]
>  __se_sys_lsetxattr fs/xattr.c:557 [inline]
>  __x64_sys_lsetxattr+0xc2/0x160 fs/xattr.c:557
>  do_syscall_64+0xdf/0x530 arch/x86/entry/common.c:298
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x459fe9
> RSP: 002b:00007fa5e54b4c08 EFLAGS: 00000246 ORIG_RAX: 00000000000000bd
> RAX: ffffffffffffffda RBX: 000000000051bf60 RCX: 0000000000459fe9
> RDX: 00000000200003c0 RSI: 0000000020000180 RDI: 0000000020000140
> RBP: 000000000051bf60 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000001009 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffc73c93fc0 R14: 000000000051bf60 R15: 00007fa5e54b4d80
> [...]
> ==================================================================
> 
> Above issue may happen as follows:
> -------------------------------------
> ext4_xattr_set
>   ext4_xattr_set_handle
>     ext4_xattr_ibody_find
>       >> s->end < s->base
>       >> no EXT4_STATE_XATTR
>       >> xattr_check_inode is not executed
>     ext4_xattr_ibody_set
>       ext4_xattr_set_entry
>        >> size_t min_offs = s->end - s->base
>        >> UAF in memcpy
> 
> we can easily reproduce this problem with the following commands:
>     mkfs.ext4 -F /dev/sda
>     mount -o debug_want_extra_isize=128 /dev/sda /mnt
>     touch /mnt/file
>     setfattr -n user.cat -v `seq -s z 4096|tr -d '[:digit:]'` /mnt/file
> 
> In ext4_xattr_ibody_find, we have the following assignment logic:
>   header = IHDR(inode, raw_inode)
>          = raw_inode + EXT4_GOOD_OLD_INODE_SIZE + i_extra_isize
>   is->s.base = IFIRST(header)
>              = header + sizeof(struct ext4_xattr_ibody_header)
>   is->s.end = raw_inode + s_inode_size
> 
> Obviously, when the inode does not have EXT4_status_XATTR and its
> i_extra_isize is large, is->s.end may be larger than is->s.base.
> In this case, the above issue may be triggered.
> 
>    EXT4_GOOD_OLD_INODE_SIZE  extra_isize  header   entry   pad   data
> |---------------------------|------------|------|---------|---|--------|
> 
> As shown above, when adding an xattr to an inode, we must ensure that the
> inode_size is not less than EXT4_GOOD_OLD_INODE_SIZE + extra_isize + pad.
> 
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Baokun Li <libaokun1@huawei.com>

Thanks for the fix! It looks good to me. Just one small nit:

> +#define INODE_HAVE_XATTR_SPACE(inode)					\
> +	((EXT4_I(inode)->i_extra_isize != 0) &&				\
> +	 (EXT4_GOOD_OLD_INODE_SIZE + EXT4_I(inode)->i_extra_isize +	\
> +	  sizeof(struct ext4_xattr_ibody_header) + EXT4_XATTR_PAD <=	\
> +	  EXT4_INODE_SIZE((inode)->i_sb)))
> +

We should have ext4 in the name of the above macro so something like:

EXT4_INODE_HAS_XATTR_SPACE()

With that fixed feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza
Baokun Li June 14, 2022, 10:01 a.m. UTC | #2 
在 2022/6/14 17:54, Jan Kara 写道:
> On Thu 02-06-22 19:46:51, Baokun Li wrote:
>> Hulk Robot reported a issue:
>> ==================================================================
>> BUG: KASAN: use-after-free in ext4_xattr_set_entry+0x18ab/0x3500
>> Write of size 4105 at addr ffff8881675ef5f4 by task syz-executor.0/7092
>>
>> CPU: 1 PID: 7092 Comm: syz-executor.0 Not tainted 4.19.90-dirty #17
>> Call Trace:
>> [...]
>>   memcpy+0x34/0x50 mm/kasan/kasan.c:303
>>   ext4_xattr_set_entry+0x18ab/0x3500 fs/ext4/xattr.c:1747
>>   ext4_xattr_ibody_inline_set+0x86/0x2a0 fs/ext4/xattr.c:2205
>>   ext4_xattr_set_handle+0x940/0x1300 fs/ext4/xattr.c:2386
>>   ext4_xattr_set+0x1da/0x300 fs/ext4/xattr.c:2498
>>   __vfs_setxattr+0x112/0x170 fs/xattr.c:149
>>   __vfs_setxattr_noperm+0x11b/0x2a0 fs/xattr.c:180
>>   __vfs_setxattr_locked+0x17b/0x250 fs/xattr.c:238
>>   vfs_setxattr+0xed/0x270 fs/xattr.c:255
>>   setxattr+0x235/0x330 fs/xattr.c:520
>>   path_setxattr+0x176/0x190 fs/xattr.c:539
>>   __do_sys_lsetxattr fs/xattr.c:561 [inline]
>>   __se_sys_lsetxattr fs/xattr.c:557 [inline]
>>   __x64_sys_lsetxattr+0xc2/0x160 fs/xattr.c:557
>>   do_syscall_64+0xdf/0x530 arch/x86/entry/common.c:298
>>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> RIP: 0033:0x459fe9
>> RSP: 002b:00007fa5e54b4c08 EFLAGS: 00000246 ORIG_RAX: 00000000000000bd
>> RAX: ffffffffffffffda RBX: 000000000051bf60 RCX: 0000000000459fe9
>> RDX: 00000000200003c0 RSI: 0000000020000180 RDI: 0000000020000140
>> RBP: 000000000051bf60 R08: 0000000000000001 R09: 0000000000000000
>> R10: 0000000000001009 R11: 0000000000000246 R12: 0000000000000000
>> R13: 00007ffc73c93fc0 R14: 000000000051bf60 R15: 00007fa5e54b4d80
>> [...]
>> ==================================================================
>>
>> Above issue may happen as follows:
>> -------------------------------------
>> ext4_xattr_set
>>    ext4_xattr_set_handle
>>      ext4_xattr_ibody_find
>>        >> s->end < s->base
>>        >> no EXT4_STATE_XATTR
>>        >> xattr_check_inode is not executed
>>      ext4_xattr_ibody_set
>>        ext4_xattr_set_entry
>>         >> size_t min_offs = s->end - s->base
>>         >> UAF in memcpy
>>
>> we can easily reproduce this problem with the following commands:
>>      mkfs.ext4 -F /dev/sda
>>      mount -o debug_want_extra_isize=128 /dev/sda /mnt
>>      touch /mnt/file
>>      setfattr -n user.cat -v `seq -s z 4096|tr -d '[:digit:]'` /mnt/file
>>
>> In ext4_xattr_ibody_find, we have the following assignment logic:
>>    header = IHDR(inode, raw_inode)
>>           = raw_inode + EXT4_GOOD_OLD_INODE_SIZE + i_extra_isize
>>    is->s.base = IFIRST(header)
>>               = header + sizeof(struct ext4_xattr_ibody_header)
>>    is->s.end = raw_inode + s_inode_size
>>
>> Obviously, when the inode does not have EXT4_status_XATTR and its
>> i_extra_isize is large, is->s.end may be larger than is->s.base.
>> In this case, the above issue may be triggered.
>>
>>     EXT4_GOOD_OLD_INODE_SIZE  extra_isize  header   entry   pad   data
>> |---------------------------|------------|------|---------|---|--------|
>>
>> As shown above, when adding an xattr to an inode, we must ensure that the
>> inode_size is not less than EXT4_GOOD_OLD_INODE_SIZE + extra_isize + pad.
>>
>> Reported-by: Hulk Robot <hulkci@huawei.com>
>> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> Thanks for the fix! It looks good to me. Just one small nit:
>
>> +#define INODE_HAVE_XATTR_SPACE(inode)					\
>> +	((EXT4_I(inode)->i_extra_isize != 0) &&				\
>> +	 (EXT4_GOOD_OLD_INODE_SIZE + EXT4_I(inode)->i_extra_isize +	\
>> +	  sizeof(struct ext4_xattr_ibody_header) + EXT4_XATTR_PAD <=	\
>> +	  EXT4_INODE_SIZE((inode)->i_sb)))
>> +
> We should have ext4 in the name of the above macro so something like:
>
> EXT4_INODE_HAS_XATTR_SPACE()
>
> With that fixed feel free to add:
>
> Reviewed-by: Jan Kara <jack@suse.cz>
>
> 								Honza

Thank you for your review!

I will send a patch V2 with the changes suggested by you. Thanks again!
diff mbox series

Patch

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index cff52ff6549d..b8cec7cb4b08 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -35,6 +35,9 @@  static int get_max_inline_xattr_value_size(struct inode *inode,
 	struct ext4_inode *raw_inode;
 	int free, min_offs;
 
+	if (!INODE_HAVE_XATTR_SPACE(inode))
+		return 0;
+
 	min_offs = EXT4_SB(inode->i_sb)->s_inode_size -
 			EXT4_GOOD_OLD_INODE_SIZE -
 			EXT4_I(inode)->i_extra_isize -
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3dce7d058985..714fa61d0afb 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4685,8 +4685,7 @@  static inline int ext4_iget_extra_inode(struct inode *inode,
 	__le32 *magic = (void *)raw_inode +
 			EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize;
 
-	if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize + sizeof(__le32) <=
-	    EXT4_INODE_SIZE(inode->i_sb) &&
+	if (INODE_HAVE_XATTR_SPACE(inode) &&
 	    *magic == cpu_to_le32(EXT4_XATTR_MAGIC)) {
 		ext4_set_inode_state(inode, EXT4_STATE_XATTR);
 		return ext4_find_inline_data_nolock(inode);
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 042325349098..4a63f8386910 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2176,8 +2176,9 @@  int ext4_xattr_ibody_find(struct inode *inode, struct ext4_xattr_info *i,
 	struct ext4_inode *raw_inode;
 	int error;
 
-	if (EXT4_I(inode)->i_extra_isize == 0)
+	if (!INODE_HAVE_XATTR_SPACE(inode))
 		return 0;
+
 	raw_inode = ext4_raw_inode(&is->iloc);
 	header = IHDR(inode, raw_inode);
 	is->s.base = is->s.first = IFIRST(header);
@@ -2205,8 +2206,9 @@  int ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
 	struct ext4_xattr_search *s = &is->s;
 	int error;
 
-	if (EXT4_I(inode)->i_extra_isize == 0)
+	if (!INODE_HAVE_XATTR_SPACE(inode))
 		return -ENOSPC;
+
 	error = ext4_xattr_set_entry(i, s, handle, inode, false /* is_block */);
 	if (error)
 		return error;
diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
index 77efb9a627ad..f2b299b347f9 100644
--- a/fs/ext4/xattr.h
+++ b/fs/ext4/xattr.h
@@ -95,6 +95,12 @@  struct ext4_xattr_entry {
 
 #define EXT4_ZERO_XATTR_VALUE ((void *)-1)
 
+#define INODE_HAVE_XATTR_SPACE(inode)					\
+	((EXT4_I(inode)->i_extra_isize != 0) &&				\
+	 (EXT4_GOOD_OLD_INODE_SIZE + EXT4_I(inode)->i_extra_isize +	\
+	  sizeof(struct ext4_xattr_ibody_header) + EXT4_XATTR_PAD <=	\
+	  EXT4_INODE_SIZE((inode)->i_sb)))
+
 struct ext4_xattr_info {
 	const char *name;
 	const void *value;