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Subject[PATCH 5.0 08/46] staging: erofs: fix fast symlink w/o xattr when fs xattr is on
Date
5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gao Xiang <gaoxiang25@huawei.com>

commit 7077fffcb0b0b65dc75e341306aeef4d0e7f2ec6 upstream.

Currently, this will hit a BUG_ON for these symlinks as follows:

- kernel message
------------[ cut here ]------------
kernel BUG at drivers/staging/erofs/xattr.c:59!
SMP PTI
CPU: 1 PID: 1170 Comm: getllxattr Not tainted 4.20.0-rc6+ #92
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-2.fc27 04/01/2014
RIP: 0010:init_inode_xattrs+0x22b/0x270
Code: 48 0f 45 ea f0 ff 4d 34 74 0d 41 83 4c 24 e0 01 31 c0 e9 00 fe ff ff 48 89 ef e8 e0 31 9e ff eb e9 89 e8 e9 ef fd ff ff 0f 0$
<0f> 0b 48 89 ef e8 fb f6 9c ff 48 8b 45 08 a8 01 75 24 f0 ff 4d 34
RSP: 0018:ffffa03ac026bdf8 EFLAGS: 00010246
------------[ cut here ]------------
...
Call Trace:
erofs_listxattr+0x30/0x2c0
? selinux_inode_listxattr+0x5a/0x80
? kmem_cache_alloc+0x33/0x170
? security_inode_listxattr+0x27/0x40
listxattr+0xaf/0xc0
path_listxattr+0x5a/0xa0
do_syscall_64+0x43/0xf0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
...
---[ end trace 3c24b49408dc0c72 ]---

Fix it by checking ->xattr_isize in init_inode_xattrs(),
and it also fixes improper return value -ENOTSUPP
(it should be -ENODATA if xattr is enabled) for those inodes.

Fixes: b17500a0fdba ("staging: erofs: introduce xattr & acl support")
Cc: <stable@vger.kernel.org> # 4.19+
Reported-by: Li Guifu <bluce.liguifu@huawei.com>
Tested-by: Li Guifu <bluce.liguifu@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/erofs/inode.c | 8 ++++----
drivers/staging/erofs/xattr.c | 25 ++++++++++++++++++++-----
2 files changed, 24 insertions(+), 9 deletions(-)

--- a/drivers/staging/erofs/inode.c
+++ b/drivers/staging/erofs/inode.c
@@ -185,16 +185,16 @@ static int fill_inode(struct inode *inod
/* setup the new inode */
if (S_ISREG(inode->i_mode)) {
#ifdef CONFIG_EROFS_FS_XATTR
- if (vi->xattr_isize)
- inode->i_op = &erofs_generic_xattr_iops;
+ inode->i_op = &erofs_generic_xattr_iops;
#endif
inode->i_fop = &generic_ro_fops;
} else if (S_ISDIR(inode->i_mode)) {
inode->i_op =
#ifdef CONFIG_EROFS_FS_XATTR
- vi->xattr_isize ? &erofs_dir_xattr_iops :
-#endif
+ &erofs_dir_xattr_iops;
+#else
&erofs_dir_iops;
+#endif
inode->i_fop = &erofs_dir_fops;
} else if (S_ISLNK(inode->i_mode)) {
/* by default, page_get_link is used for symlink */
--- a/drivers/staging/erofs/xattr.c
+++ b/drivers/staging/erofs/xattr.c
@@ -56,7 +56,26 @@ static int init_inode_xattrs(struct inod
return 0;

vi = EROFS_V(inode);
- BUG_ON(!vi->xattr_isize);
+
+ /*
+ * bypass all xattr operations if ->xattr_isize is not greater than
+ * sizeof(struct erofs_xattr_ibody_header), in detail:
+ * 1) it is not enough to contain erofs_xattr_ibody_header then
+ * ->xattr_isize should be 0 (it means no xattr);
+ * 2) it is just to contain erofs_xattr_ibody_header, which is on-disk
+ * undefined right now (maybe use later with some new sb feature).
+ */
+ if (vi->xattr_isize == sizeof(struct erofs_xattr_ibody_header)) {
+ errln("xattr_isize %d of nid %llu is not supported yet",
+ vi->xattr_isize, vi->nid);
+ return -ENOTSUPP;
+ } else if (vi->xattr_isize < sizeof(struct erofs_xattr_ibody_header)) {
+ if (unlikely(vi->xattr_isize)) {
+ DBG_BUGON(1);
+ return -EIO; /* xattr ondisk layout error */
+ }
+ return -ENOATTR;
+ }

sb = inode->i_sb;
sbi = EROFS_SB(sb);
@@ -422,7 +441,6 @@ static int erofs_xattr_generic_get(const
struct dentry *unused, struct inode *inode,
const char *name, void *buffer, size_t size)
{
- struct erofs_vnode *const vi = EROFS_V(inode);
struct erofs_sb_info *const sbi = EROFS_I_SB(inode);

switch (handler->flags) {
@@ -440,9 +458,6 @@ static int erofs_xattr_generic_get(const
return -EINVAL;
}

- if (!vi->xattr_isize)
- return -ENOATTR;
-
return erofs_getxattr(inode, handler->flags, name, buffer, size);
}


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