From d1c56bfdaca465bd1d0e913053a9c5cafe8b6a6c Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 3 Feb 2022 14:14:05 +0100 Subject: [PATCH 1/3] tests: fix idmapped mount_setattr test The test treated zero as a successful run when it really should treat non-zero as a successful run. A mount's idmapping can't change once it has been attached to the filesystem. Link: https://lore.kernel.org/r/20220203131411.3093040-2-brauner@kernel.org Fixes: 01eadc8dd96d ("tests: add mount_setattr() selftests") Cc: Seth Forshee Cc: Christoph Hellwig Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- tools/testing/selftests/mount_setattr/mount_setattr_test.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/mount_setattr/mount_setattr_test.c b/tools/testing/selftests/mount_setattr/mount_setattr_test.c index f31205f04ee0..8c5fea68ae67 100644 --- a/tools/testing/selftests/mount_setattr/mount_setattr_test.c +++ b/tools/testing/selftests/mount_setattr/mount_setattr_test.c @@ -1236,7 +1236,7 @@ static int get_userns_fd(unsigned long nsid, unsigned long hostid, unsigned long } /** - * Validate that an attached mount in our mount namespace can be idmapped. + * Validate that an attached mount in our mount namespace cannot be idmapped. * (The kernel enforces that the mount's mount namespace and the caller's mount * namespace match.) */ @@ -1259,7 +1259,7 @@ TEST_F(mount_setattr_idmapped, attached_mount_inside_current_mount_namespace) attr.userns_fd = get_userns_fd(0, 10000, 10000); ASSERT_GE(attr.userns_fd, 0); - ASSERT_EQ(sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr)), 0); + ASSERT_NE(sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr)), 0); ASSERT_EQ(close(attr.userns_fd), 0); ASSERT_EQ(close(open_tree_fd), 0); } From 97acd701185b13825f8ec7882345040415d46762 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 3 Feb 2022 14:14:06 +0100 Subject: [PATCH 2/3] MAINTAINERS: add entry for idmapped mounts I'd like to continue maintaining the work that was done around idmapped, make sure that I'm Cced on new patches and work that impacts the infrastructure. Link: https://lore.kernel.org/r/20220203131411.3093040-3-brauner@kernel.org Cc: Seth Forshee Cc: Christoph Hellwig Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- MAINTAINERS | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/MAINTAINERS b/MAINTAINERS index f41088418aae..0496b973bb87 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9253,6 +9253,15 @@ S: Maintained W: https://github.com/o2genum/ideapad-slidebar F: drivers/input/misc/ideapad_slidebar.c +IDMAPPED MOUNTS +M: Christian Brauner +L: linux-fsdevel@vger.kernel.org +S: Maintained +T: git git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git +F: Documentation/filesystems/idmappings.rst +F: tools/testing/selftests/mount_setattr/ +F: include/linux/mnt_idmapping.h + IDT VersaClock 5 CLOCK DRIVER M: Luca Ceresoli S: Maintained From 538f4f022a4612f969d5324ee227403c9f8b1d72 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 3 Feb 2022 14:14:07 +0100 Subject: [PATCH 3/3] fs: add kernel doc for mnt_{hold,unhold}_writers() When I introduced mnt_{hold,unhold}_writers() in commit fbdc2f6c40f6 ("fs: split out functions to hold writers") I did not add kernel doc for them. Fix this and introduce proper documentation. Link: https://lore.kernel.org/r/20220203131411.3093040-4-brauner@kernel.org Fixes: fbdc2f6c40f6 ("fs: split out functions to hold writers") Cc: Seth Forshee Cc: Christoph Hellwig Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- fs/namespace.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index 40b994a29e90..de6fae84f1a1 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -469,6 +469,24 @@ void mnt_drop_write_file(struct file *file) } EXPORT_SYMBOL(mnt_drop_write_file); +/** + * mnt_hold_writers - prevent write access to the given mount + * @mnt: mnt to prevent write access to + * + * Prevents write access to @mnt if there are no active writers for @mnt. + * This function needs to be called and return successfully before changing + * properties of @mnt that need to remain stable for callers with write access + * to @mnt. + * + * After this functions has been called successfully callers must pair it with + * a call to mnt_unhold_writers() in order to stop preventing write access to + * @mnt. + * + * Context: This function expects lock_mount_hash() to be held serializing + * setting MNT_WRITE_HOLD. + * Return: On success 0 is returned. + * On error, -EBUSY is returned. + */ static inline int mnt_hold_writers(struct mount *mnt) { mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; @@ -500,6 +518,18 @@ static inline int mnt_hold_writers(struct mount *mnt) return 0; } +/** + * mnt_unhold_writers - stop preventing write access to the given mount + * @mnt: mnt to stop preventing write access to + * + * Stop preventing write access to @mnt allowing callers to gain write access + * to @mnt again. + * + * This function can only be called after a successful call to + * mnt_hold_writers(). + * + * Context: This function expects lock_mount_hash() to be held. + */ static inline void mnt_unhold_writers(struct mount *mnt) { /*