[PATCH 3.12 194/235] posix_acl: Clear SGID bit when setting file permissions

From: Jiri Slaby
Date: Fri Jan 27 2017 - 06:32:28 EST

From: Jan Kara <jack@xxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit 073931017b49d9458aa351605b43a7e34598caef upstream.

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.

Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
fs/9p/acl.c | 40 +++++++++++++++++-----------------------
fs/btrfs/acl.c | 6 ++----
fs/ext2/acl.c | 12 ++++--------
fs/ext3/acl.c | 10 +++-------
fs/ext4/acl.c | 12 ++++--------
fs/f2fs/acl.c | 6 ++----
fs/gfs2/acl.c | 14 ++++++--------
fs/hfsplus/posix_acl.c | 4 ++--
fs/hfsplus/xattr.c | 5 +++--
fs/jffs2/acl.c | 9 ++++-----
fs/jfs/xattr.c | 5 +++--
fs/ocfs2/acl.c | 20 +++++++-------------
fs/posix_acl.c | 31 +++++++++++++++++++++++++++++++
fs/reiserfs/xattr_acl.c | 8 ++------
fs/xfs/xfs_acl.c | 15 +++++++--------
include/linux/posix_acl.h | 1 +
16 files changed, 98 insertions(+), 100 deletions(-)

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 7af425f53bee..9686c1f17653 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -320,32 +320,26 @@ 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:
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 0890c83643e9..d6d53e5e7945 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -118,11 +118,9 @@ 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;
diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
index 110b6b371a4e..48c3c2d7d261 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -206,15 +206,11 @@ 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;

diff --git a/fs/ext3/acl.c b/fs/ext3/acl.c
index dbb5ad59a7fc..2f994bbf73a7 100644
--- a/fs/ext3/acl.c
+++ b/fs/ext3/acl.c
@@ -205,15 +205,11 @@ ext3_set_acl(handle_t *handle, struct inode *inode, int type,
case ACL_TYPE_ACCESS:
name_index = EXT3_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
- error = posix_acl_equiv_mode(acl, &inode->i_mode);
+ error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (error < 0)
return error;
- else {
- inode->i_ctime = CURRENT_TIME_SEC;
- ext3_mark_inode_dirty(handle, inode);
- if (error == 0)
- acl = NULL;
- }
+ inode->i_ctime = CURRENT_TIME_SEC;
+ ext3_mark_inode_dirty(handle, inode);
}
break;

diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 39a54a0e9fe4..c844f1bfb451 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -211,15 +211,11 @@ 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;

diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index b7826ec1b470..f4fefc57ff56 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -223,12 +223,10 @@ 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;

diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
index f69ac0af5496..a61b0c2b57ab 100644
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -268,15 +268,13 @@ static int gfs2_xattr_system_set(struct dentry *dentry, const char *name,

if (type == ACL_TYPE_ACCESS) {
umode_t mode = inode->i_mode;
- error = posix_acl_equiv_mode(acl, &mode);
+ struct posix_acl *old_acl = acl;

- if (error <= 0) {
- posix_acl_release(acl);
- acl = NULL;
-
- if (error < 0)
- return error;
- }
+ error = posix_acl_update_mode(inode, &mode, &acl);
+ if (error < 0)
+ goto out_release;
+ if (!acl)
+ posix_acl_release(old_acl);

error = gfs2_set_mode(inode, mode);
if (error)
diff --git a/fs/hfsplus/posix_acl.c b/fs/hfsplus/posix_acl.c
index b609cc14c72e..9f7cc491ffb1 100644
--- a/fs/hfsplus/posix_acl.c
+++ b/fs/hfsplus/posix_acl.c
@@ -72,8 +72,8 @@ static int hfsplus_set_posix_acl(struct inode *inode,
case ACL_TYPE_ACCESS:
xattr_name = POSIX_ACL_XATTR_ACCESS;
if (acl) {
- err = posix_acl_equiv_mode(acl, &inode->i_mode);
- if (err < 0)
+ err = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+ if (err)
return err;
}
err = 0;
diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index bd8471fb9a6a..889be3fef4bc 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -69,8 +69,9 @@ static int can_set_system_xattr(struct inode *inode, const char *name,
if (IS_ERR(acl))
return PTR_ERR(acl);
if (acl) {
- err = posix_acl_equiv_mode(acl, &inode->i_mode);
- posix_acl_release(acl);
+ struct posix_acl *old_acl = acl;
+ err = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+ posix_acl_release(old_acl);
if (err < 0)
return err;
mark_inode_dirty(inode);
diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
index 223283c30111..9335b8d3cf52 100644
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -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:
diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
index d3472f4cd530..8c9b6a06dcbb 100644
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -693,8 +693,9 @@ static int can_set_system_xattr(struct inode *inode, const char *name,
return rc;
}
if (acl) {
- rc = posix_acl_equiv_mode(acl, &inode->i_mode);
- posix_acl_release(acl);
+ struct posix_acl *old_acl = acl;
+ rc = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+ posix_acl_release(old_acl);
if (rc < 0) {
printk(KERN_ERR
"posix_acl_equiv_mode returned %d\n",
diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
index b4f788e0ca31..23095b017752 100644
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -270,20 +270,14 @@ 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;
+ ret = ocfs2_acl_set_mode(inode, di_bh,
+ handle, mode);
+ if (ret)
return ret;
- else {
- if (ret == 0)
- acl = NULL;
-
- ret = ocfs2_acl_set_mode(inode, di_bh,
- handle, mode);
- if (ret)
- return ret;
-
- }
}
break;
case ACL_TYPE_DEFAULT:
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 3542f1f814e2..1da000aabb08 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -407,6 +407,37 @@ posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
}
EXPORT_SYMBOL(posix_acl_create);

+/**
+ * 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);
+
int
posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
{
diff --git a/fs/reiserfs/xattr_acl.c b/fs/reiserfs/xattr_acl.c
index 06c04f73da65..a86ad7ec7957 100644
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -288,13 +288,9 @@ 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:
diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
index 0e2f37efedd0..9c7b5ce06f4f 100644
--- a/fs/xfs/xfs_acl.c
+++ b/fs/xfs/xfs_acl.c
@@ -402,16 +402,15 @@ 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;
+ struct posix_acl *old_acl = acl;

- if (error <= 0) {
- posix_acl_release(acl);
- acl = NULL;
+ error = posix_acl_update_mode(inode, &mode, &acl);

- if (error < 0)
- return error;
- }
+ if (error)
+ goto out_release;
+ if (!acl)
+ posix_acl_release(old_acl);

error = xfs_set_mode(inode, mode);
if (error)
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index 7931efe71175..43cb8d59d0a7 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -89,6 +89,7 @@ extern int posix_acl_permission(struct inode *, const struct posix_acl *, int);
extern struct posix_acl *posix_acl_from_mode(umode_t, gfp_t);
extern int posix_acl_equiv_mode(const struct posix_acl *, umode_t *);
extern int posix_acl_create(struct posix_acl **, gfp_t, umode_t *);
+extern int posix_acl_update_mode(struct inode *, umode_t *, struct posix_acl **);
extern int posix_acl_chmod(struct posix_acl **, gfp_t, umode_t);

extern struct posix_acl *get_posix_acl(struct inode *, int);
--
2.11.0