diff options
| -rw-r--r-- | Documentation/trace/ftrace.rst | 2 | ||||
| -rw-r--r-- | fs/attr.c | 74 | ||||
| -rw-r--r-- | fs/fuse/file.c | 2 | ||||
| -rw-r--r-- | fs/inode.c | 64 | ||||
| -rw-r--r-- | fs/internal.h | 10 | ||||
| -rw-r--r-- | fs/ocfs2/file.c | 4 | ||||
| -rw-r--r-- | fs/open.c | 8 | ||||
| -rw-r--r-- | fs/overlayfs/file.c | 28 | ||||
| -rw-r--r-- | include/linux/fs.h | 4 |
9 files changed, 140 insertions, 56 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 60bceb018d6a..21f01d32c959 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -2940,7 +2940,7 @@ Produces:: bash-1994 [000] .... 4342.324898: ima_get_action <-process_measurement bash-1994 [000] .... 4342.324898: ima_match_policy <-ima_get_action bash-1994 [000] .... 4342.324899: do_truncate <-do_last - bash-1994 [000] .... 4342.324899: should_remove_suid <-do_truncate + bash-1994 [000] .... 4342.324899: setattr_should_drop_suidgid <-do_truncate bash-1994 [000] .... 4342.324899: notify_change <-do_truncate bash-1994 [000] .... 4342.324900: current_fs_time <-notify_change bash-1994 [000] .... 4342.324900: current_kernel_time <-current_fs_time diff --git a/fs/attr.c b/fs/attr.c index 1552a5f23d6b..b45f30e516fa 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -18,6 +18,70 @@ #include <linux/evm.h> #include <linux/ima.h> +#include "internal.h" + +/** + * setattr_should_drop_sgid - determine whether the setgid bit needs to be + * removed + * @mnt_userns: user namespace of the mount @inode was found from + * @inode: inode to check + * + * This function determines whether the setgid bit needs to be removed. + * We retain backwards compatibility and require setgid bit to be removed + * unconditionally if S_IXGRP is set. Otherwise we have the exact same + * requirements as setattr_prepare() and setattr_copy(). + * + * Return: ATTR_KILL_SGID if setgid bit needs to be removed, 0 otherwise. + */ +int setattr_should_drop_sgid(struct user_namespace *mnt_userns, + const struct inode *inode) +{ + umode_t mode = inode->i_mode; + + if (!(mode & S_ISGID)) + return 0; + if (mode & S_IXGRP) + return ATTR_KILL_SGID; + if (!in_group_or_capable(mnt_userns, inode, + i_gid_into_vfsgid(mnt_userns, inode))) + return ATTR_KILL_SGID; + return 0; +} + +/** + * setattr_should_drop_suidgid - determine whether the set{g,u}id bit needs to + * be dropped + * @mnt_userns: user namespace of the mount @inode was found from + * @inode: inode to check + * + * This function determines whether the set{g,u}id bits need to be removed. + * If the setuid bit needs to be removed ATTR_KILL_SUID is returned. If the + * setgid bit needs to be removed ATTR_KILL_SGID is returned. If both + * set{g,u}id bits need to be removed the corresponding mask of both flags is + * returned. + * + * Return: A mask of ATTR_KILL_S{G,U}ID indicating which - if any - setid bits + * to remove, 0 otherwise. + */ +int setattr_should_drop_suidgid(struct user_namespace *mnt_userns, + struct inode *inode) +{ + umode_t mode = inode->i_mode; + int kill = 0; + + /* suid always must be killed */ + if (unlikely(mode & S_ISUID)) + kill = ATTR_KILL_SUID; + + kill |= setattr_should_drop_sgid(mnt_userns, inode); + + if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) + return kill; + + return 0; +} +EXPORT_SYMBOL(setattr_should_drop_suidgid); + /** * chown_ok - verify permissions to chown inode * @mnt_userns: user namespace of the mount @inode was found from @@ -140,8 +204,7 @@ int setattr_prepare(struct user_namespace *mnt_userns, struct dentry *dentry, vfsgid = i_gid_into_vfsgid(mnt_userns, inode); /* Also check the setgid bit! */ - if (!vfsgid_in_group_p(vfsgid) && - !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) + if (!in_group_or_capable(mnt_userns, inode, vfsgid)) attr->ia_mode &= ~S_ISGID; } @@ -251,9 +314,8 @@ void setattr_copy(struct user_namespace *mnt_userns, struct inode *inode, inode->i_ctime = attr->ia_ctime; if (ia_valid & ATTR_MODE) { umode_t mode = attr->ia_mode; - vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode); - if (!vfsgid_in_group_p(vfsgid) && - !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) + if (!in_group_or_capable(mnt_userns, inode, + i_gid_into_vfsgid(mnt_userns, inode))) mode &= ~S_ISGID; inode->i_mode = mode; } @@ -375,7 +437,7 @@ int notify_change(struct user_namespace *mnt_userns, struct dentry *dentry, } } if (ia_valid & ATTR_KILL_SGID) { - if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { + if (mode & S_ISGID) { if (!(ia_valid & ATTR_MODE)) { ia_valid = attr->ia_valid |= ATTR_MODE; attr->ia_mode = inode->i_mode; diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 89f4741728ba..c996c0ef8c63 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1313,7 +1313,7 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from) return err; if (fc->handle_killpriv_v2 && - should_remove_suid(file_dentry(file))) { + setattr_should_drop_suidgid(&init_user_ns, file_inode(file))) { goto writethrough; } diff --git a/fs/inode.c b/fs/inode.c index 762feb8d0c6c..5ccc61fe8a1f 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -1949,40 +1949,12 @@ skip_update: EXPORT_SYMBOL(touch_atime); /* - * The logic we want is - * - * if suid or (sgid and xgrp) - * remove privs - */ -int should_remove_suid(struct dentry *dentry) -{ - umode_t mode = d_inode(dentry)->i_mode; - int kill = 0; - - /* suid always must be killed */ - if (unlikely(mode & S_ISUID)) - kill = ATTR_KILL_SUID; - - /* - * sgid without any exec bits is just a mandatory locking mark; leave - * it alone. If some exec bits are set, it's a real sgid; kill it. - */ - if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) - kill |= ATTR_KILL_SGID; - - if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) - return kill; - - return 0; -} -EXPORT_SYMBOL(should_remove_suid); - -/* * Return mask of changes for notify_change() that need to be done as a * response to write or truncate. Return 0 if nothing has to be changed. * Negative value on error (change should be denied). */ -int dentry_needs_remove_privs(struct dentry *dentry) +int dentry_needs_remove_privs(struct user_namespace *mnt_userns, + struct dentry *dentry) { struct inode *inode = d_inode(dentry); int mask = 0; @@ -1991,7 +1963,7 @@ int dentry_needs_remove_privs(struct dentry *dentry) if (IS_NOSEC(inode)) return 0; - mask = should_remove_suid(dentry); + mask = setattr_should_drop_suidgid(mnt_userns, inode); ret = security_inode_need_killpriv(dentry); if (ret < 0) return ret; @@ -2023,7 +1995,7 @@ static int __file_remove_privs(struct file *file, unsigned int flags) if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode)) return 0; - kill = dentry_needs_remove_privs(dentry); + kill = dentry_needs_remove_privs(file_mnt_user_ns(file), dentry); if (kill < 0) return kill; @@ -2485,6 +2457,28 @@ struct timespec64 current_time(struct inode *inode) EXPORT_SYMBOL(current_time); /** + * in_group_or_capable - check whether caller is CAP_FSETID privileged + * @mnt_userns: user namespace of the mount @inode was found from + * @inode: inode to check + * @vfsgid: the new/current vfsgid of @inode + * + * Check wether @vfsgid is in the caller's group list or if the caller is + * privileged with CAP_FSETID over @inode. This can be used to determine + * whether the setgid bit can be kept or must be dropped. + * + * Return: true if the caller is sufficiently privileged, false if not. + */ +bool in_group_or_capable(struct user_namespace *mnt_userns, + const struct inode *inode, vfsgid_t vfsgid) +{ + if (vfsgid_in_group_p(vfsgid)) + return true; + if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) + return true; + return false; +} + +/** * mode_strip_sgid - handle the sgid bit for non-directories * @mnt_userns: User namespace of the mount the inode was created from * @dir: parent directory inode @@ -2505,11 +2499,9 @@ umode_t mode_strip_sgid(struct user_namespace *mnt_userns, return mode; if (S_ISDIR(mode) || !dir || !(dir->i_mode & S_ISGID)) return mode; - if (in_group_p(i_gid_into_mnt(mnt_userns, dir))) - return mode; - if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID)) + if (in_group_or_capable(mnt_userns, dir, + i_gid_into_vfsgid(mnt_userns, dir))) return mode; - return mode & ~S_ISGID; } EXPORT_SYMBOL(mode_strip_sgid); diff --git a/fs/internal.h b/fs/internal.h index e377eb7bbe7f..0c8812fe7ca4 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -150,7 +150,9 @@ extern int vfs_open(const struct path *, struct file *); * inode.c */ extern long prune_icache_sb(struct super_block *sb, struct shrink_control *sc); -extern int dentry_needs_remove_privs(struct dentry *dentry); +int dentry_needs_remove_privs(struct user_namespace *, struct dentry *dentry); +bool in_group_or_capable(struct user_namespace *mnt_userns, + const struct inode *inode, vfsgid_t vfsgid); /* * fs-writeback.c @@ -255,3 +257,9 @@ static inline ssize_t do_get_acl(struct user_namespace *mnt_userns, #endif ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos); + +/* + * fs/attr.c + */ +int setattr_should_drop_sgid(struct user_namespace *mnt_userns, + const struct inode *inode); diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c index af900aaa9275..5c60b6bc85bf 100644 --- a/fs/ocfs2/file.c +++ b/fs/ocfs2/file.c @@ -1991,7 +1991,7 @@ static int __ocfs2_change_file_space(struct file *file, struct inode *inode, } } - if (file && should_remove_suid(file->f_path.dentry)) { + if (file && setattr_should_drop_suidgid(&init_user_ns, file_inode(file))) { ret = __ocfs2_write_remove_suid(inode, di_bh); if (ret) { mlog_errno(ret); @@ -2279,7 +2279,7 @@ static int ocfs2_prepare_inode_for_write(struct file *file, * inode. There's also the dinode i_size state which * can be lost via setattr during extending writes (we * set inode->i_size at the end of a write. */ - if (should_remove_suid(dentry)) { + if (setattr_should_drop_suidgid(&init_user_ns, inode)) { if (meta_level == 0) { ocfs2_inode_unlock_for_extent_tree(inode, &di_bh, diff --git a/fs/open.c b/fs/open.c index a81319b6177f..9d0197db15e7 100644 --- a/fs/open.c +++ b/fs/open.c @@ -54,7 +54,7 @@ int do_truncate(struct user_namespace *mnt_userns, struct dentry *dentry, } /* Remove suid, sgid, and file capabilities on truncate too */ - ret = dentry_needs_remove_privs(dentry); + ret = dentry_needs_remove_privs(mnt_userns, dentry); if (ret < 0) return ret; if (ret) @@ -723,10 +723,10 @@ retry_deleg: return -EINVAL; if ((group != (gid_t)-1) && !setattr_vfsgid(&newattrs, gid)) return -EINVAL; - if (!S_ISDIR(inode->i_mode)) - newattrs.ia_valid |= - ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV; inode_lock(inode); + if (!S_ISDIR(inode->i_mode)) + newattrs.ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV | + setattr_should_drop_sgid(mnt_userns, inode); /* Continue to send actual fs values, not the mount values. */ error = security_path_chown( path, diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index a1a22f58ba18..d066be3b9226 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -517,9 +517,16 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len const struct cred *old_cred; int ret; + inode_lock(inode); + /* Update mode */ + ovl_copyattr(inode); + ret = file_remove_privs(file); + if (ret) + goto out_unlock; + ret = ovl_real_fdget(file, &real); if (ret) - return ret; + goto out_unlock; old_cred = ovl_override_creds(file_inode(file)->i_sb); ret = vfs_fallocate(real.file, mode, offset, len); @@ -530,6 +537,9 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len fdput(real); +out_unlock: + inode_unlock(inode); + return ret; } @@ -567,14 +577,23 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in, const struct cred *old_cred; loff_t ret; + inode_lock(inode_out); + if (op != OVL_DEDUPE) { + /* Update mode */ + ovl_copyattr(inode_out); + ret = file_remove_privs(file_out); + if (ret) + goto out_unlock; + } + ret = ovl_real_fdget(file_out, &real_out); if (ret) - return ret; + goto out_unlock; ret = ovl_real_fdget(file_in, &real_in); if (ret) { fdput(real_out); - return ret; + goto out_unlock; } old_cred = ovl_override_creds(file_inode(file_out)->i_sb); @@ -603,6 +622,9 @@ static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in, fdput(real_in); fdput(real_out); +out_unlock: + inode_unlock(inode_out); + return ret; } diff --git a/include/linux/fs.h b/include/linux/fs.h index d1347311010c..effa4a2e5098 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3133,7 +3133,7 @@ extern void __destroy_inode(struct inode *); extern struct inode *new_inode_pseudo(struct super_block *sb); extern struct inode *new_inode(struct super_block *sb); extern void free_inode_nonrcu(struct inode *inode); -extern int should_remove_suid(struct dentry *); +extern int setattr_should_drop_suidgid(struct user_namespace *, struct inode *); extern int file_remove_privs(struct file *); /* @@ -3564,7 +3564,7 @@ int __init list_bdev_fs_names(char *buf, size_t size); static inline bool is_sxid(umode_t mode) { - return (mode & S_ISUID) || ((mode & S_ISGID) && (mode & S_IXGRP)); + return mode & (S_ISUID | S_ISGID); } static inline int check_sticky(struct user_namespace *mnt_userns, |