From: Baokun Li libaokun1@huawei.com
hulk inclusion category: bugfix bugzilla: 186866, https://gitee.com/openeuler/kernel/issues/I5DTBL CVE: NA
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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. Otherwise, the end position may be greater than the start position, resulting in UAF.
Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- fs/ext4/xattr.h | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h index f39cad2abe2a..990084e00374 100644 --- a/fs/ext4/xattr.h +++ b/fs/ext4/xattr.h @@ -95,6 +95,19 @@ struct ext4_xattr_entry {
#define EXT4_ZERO_XATTR_VALUE ((void *)-1)
+/* + * If we want to add an xattr to the inode, we should make sure that + * i_extra_isize is not 0 and that the inode size is not less than + * EXT4_GOOD_OLD_INODE_SIZE + extra_isize + pad. + * EXT4_GOOD_OLD_INODE_SIZE extra_isize header entry pad data + * |--------------------------|------------|------|---------|---|-------| + */ +#define EXT4_INODE_HAS_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;
From: Baokun Li libaokun1@huawei.com
hulk inclusion category: bugfix bugzilla: 186866, https://gitee.com/openeuler/kernel/issues/I5DTBL CVE: NA
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Hulk Robot reported a issue: Reviewed-by: Zhang Yi yi.zhang@huawei.com
================================================================== 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
In ext4_xattr_set_entry min_offs = s->end - s->base = s_inode_size - EXT4_GOOD_OLD_INODE_SIZE - i_extra_isize - sizeof(struct ext4_xattr_ibody_header) last = s->first free = min_offs - ((void *)last - s->base) - sizeof(__u32) = s_inode_size - EXT4_GOOD_OLD_INODE_SIZE - i_extra_isize - sizeof(struct ext4_xattr_ibody_header) - sizeof(__u32)
In the calculation formula, all values except s_inode_size and i_extra_size are fixed values. When i_extra_size is the maximum value s_inode_size - EXT4_GOOD_OLD_INODE_SIZE, min_offs is -4 and free is -8. The value overflows. As a result, the preceding issue is triggered when memcpy is executed.
Therefore, when finding xattr or setting xattr, check whether there is space for storing xattr in the inode to resolve this issue.
Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Baokun Li libaokun1@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- fs/ext4/xattr.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 9217e89a65d9..ffaf31584c0e 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -2171,8 +2171,9 @@ 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 (!EXT4_INODE_HAS_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); @@ -2200,8 +2201,9 @@ int ext4_xattr_ibody_inline_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 (!EXT4_INODE_HAS_XATTR_SPACE(inode)) return -ENOSPC; + error = ext4_xattr_set_entry(i, s, handle, inode, false /* is_block */); if (error) return error; @@ -2224,8 +2226,9 @@ static 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 (!EXT4_INODE_HAS_XATTR_SPACE(inode)) return -ENOSPC; + error = ext4_xattr_set_entry(i, s, handle, inode, false /* is_block */); if (error) return error;
From: Baokun Li libaokun1@huawei.com
hulk inclusion category: bugfix bugzilla: 186866, https://gitee.com/openeuler/kernel/issues/I5DTBL CVE: NA
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If the ext4 inode does not have xattr space, 0 is returned in the get_max_inline_xattr_value_size function. Otherwise, the function returns a negative value when the inode does not contain EXT4_STATE_XATTR.
Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- fs/ext4/inline.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 6d868ede1d11..f1473717863e 100644 --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -34,6 +34,9 @@ static int get_max_inline_xattr_value_size(struct inode *inode, struct ext4_inode *raw_inode; int free, min_offs;
+ if (!EXT4_INODE_HAS_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 -
From: Baokun Li libaokun1@huawei.com
hulk inclusion category: bugfix bugzilla: 186866, https://gitee.com/openeuler/kernel/issues/I5DTBL CVE: NA
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Use the EXT4_INODE_HAS_XATTR_SPACE macro to more accurately determine whether the inode have xattr space.
Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- fs/ext4/inode.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 61e1b3d6cf35..5d198b0171ab 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4933,8 +4933,7 @@ 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 (EXT4_INODE_HAS_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);
-
Yongqiang Liu