On 2018/12/26 17:31, Gao Xiang wrote:
> 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")
> Reported-by: Li Guifu <[email protected]>
> Signed-off-by: Gao Xiang <[email protected]>
> ---
> drivers/staging/erofs/inode.c | 8 ++++----
> drivers/staging/erofs/xattr.c | 17 ++++++++++++-----
> 2 files changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/staging/erofs/inode.c b/drivers/staging/erofs/inode.c
> index d7fbf5f4600f..f99954dbfdb5 100644
> --- a/drivers/staging/erofs/inode.c
> +++ b/drivers/staging/erofs/inode.c
> @@ -185,16 +185,16 @@ static int fill_inode(struct inode *inode, int isdir)
> /* 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 */
> diff --git a/drivers/staging/erofs/xattr.c b/drivers/staging/erofs/xattr.c
> index 80dca6a4adbe..c15f33637ba8 100644
> --- a/drivers/staging/erofs/xattr.c
> +++ b/drivers/staging/erofs/xattr.c
> @@ -56,7 +56,18 @@ static int init_inode_xattrs(struct inode *inode)
> return 0;
>
> vi = EROFS_V(inode);
> - BUG_ON(!vi->xattr_isize);
> +
> + /*
> + * bypass all xattr operations if vi->xattr_isize is not enough to
> + * contain erofs_xattr_ibody_header (and it should only be 0).
> + */
> + 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 +433,6 @@ static int erofs_xattr_generic_get(const struct
> xattr_handler *handler,
> 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 +450,6 @@ static int erofs_xattr_generic_get(const struct
> xattr_handler *handler,
> return -EINVAL;
> }
>
> - if (!vi->xattr_isize)
> - return -ENOATTR;
> -
> return erofs_getxattr(inode, handler->flags, name, buffer, size);
> }
>
It fixed the issue, confirmed at Linux buildroot 4.20-rc5+
Tested-by Li Guifu <[email protected]>
thanks
