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Thu, 29 Oct 2020 00:35:46 +0000 From: Christian Brauner To: Alexander Viro , Christoph Hellwig , linux-fsdevel@vger.kernel.org Subject: [PATCH 20/34] open: handle idmapped mounts in do_truncate() Date: Thu, 29 Oct 2020 01:32:38 +0100 Message-Id: <20201029003252.2128653-21-christian.brauner@ubuntu.com> In-Reply-To: <20201029003252.2128653-1-christian.brauner@ubuntu.com> References: <20201029003252.2128653-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-loop: linux-audit@redhat.com X-Mailman-Approved-At: Thu, 29 Oct 2020 08:45:20 -0400 Cc: Phil Estes , Lennart Poettering , Amir Goldstein , Mimi Zohar , James Bottomley , Andreas Dilger , containers@lists.linux-foundation.org, Christian Brauner , Tycho Andersen , Miklos Szeredi , James Morris , smbarber@chromium.org, linux-ext4@vger.kernel.org, Mrunal Patel , Serge Hallyn , Arnd Bergmann , Jann Horn , selinux@vger.kernel.org, Josh Triplett , Seth Forshee , Aleksa Sarai , Andy Lutomirski , OGAWA Hirofumi , Geoffrey Thomas , David Howells , John Johansen , Theodore Tso , Dmitry Kasatkin , Jonathan Corbet , linux-unionfs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-audit@redhat.com, "Eric W. Biederman" , linux-api@vger.kernel.org, Alban Crequy , linux-integrity@vger.kernel.org, =?UTF-8?q?St=C3=A9phane=20Graber?= , Todd Kjos X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=linux-audit-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit When truncating files the vfs will verify that the caller is privileged over the inode. Since the do_truncate() helper is only used in a few places in the vfs code extend it to handle idmapped mounts instead of adding a new helper. If the inode is accessed through an idmapped mount it is mapped according to the mount's user namespace. Afterwards the permissions checks are identical to non-idmapped mounts. If the initial user namespace is passed all mapping operations are a nop so non-idmapped mounts will not see a change in behavior and will also not see any performance impact. Signed-off-by: Christian Brauner --- fs/coredump.c | 12 +++++++++--- fs/inode.c | 13 +++++++++---- fs/namei.c | 6 +++--- fs/open.c | 21 +++++++++++++-------- include/linux/fs.h | 4 ++-- 5 files changed, 36 insertions(+), 20 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 0cd9056d79cc..25beac7230ff 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -703,6 +703,7 @@ void do_coredump(const kernel_siginfo_t *siginfo) goto close_fail; } } else { + struct user_namespace *user_ns; struct inode *inode; int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW | O_LARGEFILE | O_EXCL; @@ -786,7 +787,8 @@ void do_coredump(const kernel_siginfo_t *siginfo) goto close_fail; if (!(cprm.file->f_mode & FMODE_CAN_WRITE)) goto close_fail; - if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file)) + user_ns = mnt_user_ns(cprm.file->f_path.mnt); + if (do_truncate(user_ns, cprm.file->f_path.dentry, 0, 0, cprm.file)) goto close_fail; } @@ -931,8 +933,12 @@ void dump_truncate(struct coredump_params *cprm) if (file->f_op->llseek && file->f_op->llseek != no_llseek) { offset = file->f_op->llseek(file, 0, SEEK_CUR); - if (i_size_read(file->f_mapping->host) < offset) - do_truncate(file->f_path.dentry, offset, 0, file); + if (i_size_read(file->f_mapping->host) < offset) { + struct user_namespace *user_ns; + + user_ns = mnt_user_ns(file->f_path.mnt); + do_truncate(user_ns, file->f_path.dentry, offset, 0, file); + } } } EXPORT_SYMBOL(dump_truncate); diff --git a/fs/inode.c b/fs/inode.c index 22de3cb3b1f4..a9e2c8232e61 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -1904,7 +1904,8 @@ int dentry_needs_remove_privs(struct dentry *dentry) return mask; } -static int __remove_privs(struct dentry *dentry, int kill) +static int __remove_privs(struct user_namespace *user_ns, struct dentry *dentry, + int kill) { struct iattr newattrs; @@ -1913,7 +1914,7 @@ static int __remove_privs(struct dentry *dentry, int kill) * Note we call this on write, so notify_change will not * encounter any conflicting delegations: */ - return notify_change(dentry, &newattrs, NULL); + return notify_mapped_change(user_ns, dentry, &newattrs, NULL); } /* @@ -1939,8 +1940,12 @@ int file_remove_privs(struct file *file) kill = dentry_needs_remove_privs(dentry); if (kill < 0) return kill; - if (kill) - error = __remove_privs(dentry, kill); + if (kill) { + struct user_namespace *user_ns; + + user_ns = mnt_user_ns(file->f_path.mnt); + error = __remove_privs(user_ns, dentry, kill); + } if (!error) inode_has_no_xattr(inode); diff --git a/fs/namei.c b/fs/namei.c index 7901ea09e80e..76c9637eccb9 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2985,9 +2985,9 @@ static int handle_truncate(struct file *filp) if (!error) error = security_path_truncate(path); if (!error) { - error = do_truncate(path->dentry, 0, - ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, - filp); + error = do_truncate(mnt_user_ns(filp->f_path.mnt), + path->dentry, 0, + ATTR_MTIME | ATTR_CTIME | ATTR_OPEN, filp); } put_write_access(inode); return error; diff --git a/fs/open.c b/fs/open.c index 9af548fb841b..efa462b6b9c7 100644 --- a/fs/open.c +++ b/fs/open.c @@ -35,8 +35,8 @@ #include "internal.h" -int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs, - struct file *filp) +int do_truncate(struct user_namespace *user_ns, struct dentry *dentry, + loff_t length, unsigned int time_attrs, struct file *filp) { int ret; struct iattr newattrs; @@ -61,13 +61,14 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs, inode_lock(dentry->d_inode); /* Note any delegations or leases have already been broken: */ - ret = notify_change(dentry, &newattrs, NULL); + ret = notify_mapped_change(user_ns, dentry, &newattrs, NULL); inode_unlock(dentry->d_inode); return ret; } long vfs_truncate(const struct path *path, loff_t length) { + struct user_namespace *user_ns; struct inode *inode; long error; @@ -83,7 +84,8 @@ long vfs_truncate(const struct path *path, loff_t length) if (error) goto out; - error = inode_permission(inode, MAY_WRITE); + user_ns = mnt_user_ns(path->mnt); + error = mapped_inode_permission(user_ns, inode, MAY_WRITE); if (error) goto mnt_drop_write_and_out; @@ -107,7 +109,7 @@ long vfs_truncate(const struct path *path, loff_t length) if (!error) error = security_path_truncate(path); if (!error) - error = do_truncate(path->dentry, length, 0, NULL); + error = do_truncate(user_ns, path->dentry, length, 0, NULL); put_write_and_out: put_write_access(inode); @@ -186,13 +188,16 @@ long do_sys_ftruncate(unsigned int fd, loff_t length, int small) /* Check IS_APPEND on real upper inode */ if (IS_APPEND(file_inode(f.file))) goto out_putf; - sb_start_write(inode->i_sb); error = locks_verify_truncate(inode, f.file, length); if (!error) error = security_path_truncate(&f.file->f_path); - if (!error) - error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file); + if (!error) { + struct user_namespace *user_ns; + + user_ns = mnt_user_ns(f.file->f_path.mnt); + error = do_truncate(user_ns, dentry, length, ATTR_MTIME | ATTR_CTIME, f.file); + } sb_end_write(inode->i_sb); out_putf: fdput(f); diff --git a/include/linux/fs.h b/include/linux/fs.h index f523b1db48c4..bfcfa3d7374f 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2610,8 +2610,8 @@ struct filename { static_assert(offsetof(struct filename, iname) % sizeof(long) == 0); extern long vfs_truncate(const struct path *, loff_t); -extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs, - struct file *filp); +extern int do_truncate(struct user_namespace *, struct dentry *, loff_t start, + unsigned int time_attrs, struct file *filp); extern int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len); extern long do_sys_open(int dfd, const char __user *filename, int flags, -- 2.29.0 -- Linux-audit mailing list Linux-audit@redhat.com https://www.redhat.com/mailman/listinfo/linux-audit