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posix_acl: Clear SGID bit when setting file permissions 

When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok().  Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2).  Fix that.

References: CVE-2016-7097
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/
linux.git
Git-commit: 073931017b49d9458aa351605b43a7e34598caef
Change-Id: Idf7cd8d0fb030fedeabd46254e4c4a9c08bce8b5
[d-cagle@codeaurora.org: Resolve merge conflicts and style]
Signed-off-by: Dennis Cagle <d-cagle@codeaurora.org>
[stummala@codeaurora.org: Resolve merge conflicts on existing files and
skip files fs/ceph/acl.c, fs/hfsplus/posix_acl.c and fs/jfs/acl.c from
original change as those files are not present/fix is not applicable on
3.10 kernel]
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
This commit is contained in:
Jan Kara 2016-09-19 17:39:09 +02:00 committed by Gerrit - the friendly Code Review server
parent 067816447b
commit 1f26976892
12 changed files with 85 additions and 66 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
fs/9p/acl.c
View File

@ -320,32 +320,27 @@ static int v9fs_xattr_set_acl(struct dentry *dentry, const char *name,
case ACL_TYPE_ACCESS:
name = POSIX_ACL_XATTR_ACCESS;
if (acl) {
umode_t mode = inode->i_mode;
retval = posix_acl_equiv_mode(acl, &mode);
if (retval < 0)
struct iattr iattr;
retval = posix_acl_update_mode(inode,
&iattr.ia_mode, &acl);
if (retval)
goto err_out;
else {
struct iattr iattr;
if (retval == 0) {
/*
* ACL can be represented
* by the mode bits. So don't
* update ACL.
*/
acl = NULL;
value = NULL;
size = 0;
}
/* Updte the mode bits */
iattr.ia_mode = ((mode & S_IALLUGO) |
(inode->i_mode & ~S_IALLUGO));
iattr.ia_valid = ATTR_MODE;
/* FIXME should we update ctime ?
* What is the following setxattr update the
* mode ?
if (!acl) {
/*
* ACL can be represented
* by the mode bits. So don't
* update ACL.
*/
v9fs_vfs_setattr_dotl(dentry, &iattr);
value = NULL;
size = 0;
}
iattr.ia_valid = ATTR_MODE;
/* FIXME should we update ctime ?
* What is the following setxattr update the
* mode ?
*/
v9fs_vfs_setattr_dotl(dentry, &iattr);
}
break;
case ACL_TYPE_DEFAULT:

7
fs/btrfs/acl.c
View File

@ -118,11 +118,10 @@ static int btrfs_set_acl(struct btrfs_trans_handle *trans,
case ACL_TYPE_ACCESS:
name = POSIX_ACL_XATTR_ACCESS;
if (acl) {
ret = posix_acl_equiv_mode(acl, &inode->i_mode);
if (ret < 0)
ret = posix_acl_update_mode(inode,
&inode->i_mode, &acl);
if (ret)
return ret;
if (ret == 0)
acl = NULL;
}
ret = 0;
break;

13
fs/ext2/acl.c
View File

@ -206,15 +206,12 @@ ext2_set_acl(struct inode *inode, int type, struct posix_acl *acl)
case ACL_TYPE_ACCESS:
name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode,
&inode->i_mode, &acl);
if (error)
return error;
else {
inode->i_ctime = CURRENT_TIME_SEC;
mark_inode_dirty(inode);
if (error == 0)
acl = NULL;
}
inode->i_ctime = CURRENT_TIME_SEC;
mark_inode_dirty(inode);
}
break;

13
fs/ext4/acl.c
View File

@ -211,15 +211,12 @@ ext4_set_acl(handle_t *handle, struct inode *inode, int type,
case ACL_TYPE_ACCESS:
name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode,
&inode->i_mode, &acl);
if (error)
return error;
else {
inode->i_ctime = ext4_current_time(inode);
ext4_mark_inode_dirty(handle, inode);
if (error == 0)
acl = NULL;
}
inode->i_ctime = ext4_current_time(inode);
ext4_mark_inode_dirty(handle, inode);
}
break;

7
fs/f2fs/acl.c
View File

@ -223,12 +223,11 @@ static int f2fs_set_acl(struct inode *inode, int type, struct posix_acl *acl)
case ACL_TYPE_ACCESS:
name_index = F2FS_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode,
&inode->i_mode, &acl);
if (error)
return error;
set_acl_inode(fi, inode->i_mode);
if (error == 0)
acl = NULL;
}
break;

5
fs/gfs2/acl.c
View File

@ -267,8 +267,9 @@ static int gfs2_xattr_system_set(struct dentry *dentry, const char *name,
goto out_release;
if (type == ACL_TYPE_ACCESS) {
umode_t mode = inode->i_mode;
error = posix_acl_equiv_mode(acl, &mode);
umode_t mode;
error = posix_acl_update_mode(inode, &mode, &acl);
if (error <= 0) {
posix_acl_release(acl);

9
fs/jffs2/acl.c
View File

@ -243,9 +243,10 @@ static int jffs2_set_acl(struct inode *inode, int type, struct posix_acl *acl)
case ACL_TYPE_ACCESS:
xprefix = JFFS2_XPREFIX_ACL_ACCESS;
if (acl) {
umode_t mode = inode->i_mode;
rc = posix_acl_equiv_mode(acl, &mode);
if (rc < 0)
umode_t mode;
rc = posix_acl_update_mode(inode, &mode, &acl);
if (rc)
return rc;
if (inode->i_mode != mode) {
struct iattr attr;
@ -257,8 +258,6 @@ static int jffs2_set_acl(struct inode *inode, int type, struct posix_acl *acl)
if (rc < 0)
return rc;
}
if (rc == 0)
acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:

8
fs/ocfs2/acl.c
View File

@ -274,9 +274,10 @@ static int ocfs2_set_acl(handle_t *handle,
case ACL_TYPE_ACCESS:
name_index = OCFS2_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
umode_t mode = inode->i_mode;
ret = posix_acl_equiv_mode(acl, &mode);
if (ret < 0)
umode_t mode;
ret = posix_acl_update_mode(inode, &mode, &acl);
if (ret)
return ret;
else {
if (ret == 0)
@ -286,7 +287,6 @@ static int ocfs2_set_acl(handle_t *handle,
handle, mode);
if (ret)
return ret;
}
}
break;

31
fs/posix_acl.c
View File

@ -424,3 +424,34 @@ posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
return err;
}
EXPORT_SYMBOL(posix_acl_chmod);
/**
* posix_acl_update_mode - update mode in set_acl
*
* Update the file mode when setting an ACL: compute the new file permission
* bits based on the ACL. In addition, if the ACL is equivalent to the new
* file mode, set *acl to NULL to indicate that no ACL should be set.
*
* As with chmod, clear the setgit bit if the caller is not in the owning group
* or capable of CAP_FSETID (see inode_change_ok).
*
* Called from set_acl inode operations.
*/
int posix_acl_update_mode(struct inode *inode, umode_t *mode_p,
struct posix_acl **acl)
{
umode_t mode = inode->i_mode;
int error;
error = posix_acl_equiv_mode(*acl, &mode);
if (error < 0)
return error;
if (error == 0)
*acl = NULL;
if (!in_group_p(inode->i_gid) &&
!capable_wrt_inode_uidgid(inode, CAP_FSETID))
mode &= ~S_ISGID;
*mode_p = mode;
return 0;
}
EXPORT_SYMBOL(posix_acl_update_mode);

9
fs/reiserfs/xattr_acl.c
View File

@ -286,13 +286,10 @@ reiserfs_set_acl(struct reiserfs_transaction_handle *th, struct inode *inode,
case ACL_TYPE_ACCESS:
name = POSIX_ACL_XATTR_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode,
&inode->i_mode, &acl);
if (error)
return error;
else {
if (error == 0)
acl = NULL;
}
}
break;
case ACL_TYPE_DEFAULT:

5
fs/xfs/xfs_acl.c
View File

@ -388,8 +388,9 @@ xfs_xattr_acl_set(struct dentry *dentry, const char *name,
goto out_release;
if (type == ACL_TYPE_ACCESS) {
umode_t mode = inode->i_mode;
error = posix_acl_equiv_mode(acl, &mode);
umode_t mode;
error = posix_acl_update_mode(inode, &mode, &acl);
if (error <= 0) {
posix_acl_release(acl);

3
include/linux/posix_acl.h
View File

@ -95,6 +95,9 @@ extern struct posix_acl *get_posix_acl(struct inode *, int);
extern int set_posix_acl(struct inode *, int, struct posix_acl *);
#ifdef CONFIG_FS_POSIX_ACL
extern int posix_acl_update_mode(struct inode *, umode_t *,
struct posix_acl **);
static inline struct posix_acl **acl_by_type(struct inode *inode, int type)
{
switch (type) {