This is a note to let you know that I've just added the patch titled attr: add setattr_should_drop_sgid() to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: attr-add-setattr_should_drop_sgid.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From stable-owner@xxxxxxxxxxxxxxx Sat Mar 18 11:16:16 2023 From: Amir Goldstein <amir73il@xxxxxxxxx> Date: Sat, 18 Mar 2023 12:15:26 +0200 Subject: attr: add setattr_should_drop_sgid() To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Sasha Levin <sashal@xxxxxxxxxx>, "Darrick J . Wong" <djwong@xxxxxxxxxx>, Leah Rumancik <leah.rumancik@xxxxxxxxx>, Chandan Babu R <chandan.babu@xxxxxxxxxx>, Christian Brauner <brauner@xxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-xfs@xxxxxxxxxxxxxxx, stable@xxxxxxxxxxxxxxx Message-ID: <20230318101529.1361673-13-amir73il@xxxxxxxxx> From: Amir Goldstein <amir73il@xxxxxxxxx> commit 72ae017c5451860443a16fb2a8c243bff3e396b8 upstream. [backported to 5.10.y, prior to idmapped mounts] The current setgid stripping logic during write and ownership change operations is inconsistent and strewn over multiple places. In order to consolidate it and make more consistent we'll add a new helper setattr_should_drop_sgid(). The function retains the old behavior where we remove the S_ISGID bit unconditionally when S_IXGRP is set but also when it isn't set and the caller is neither in the group of the inode nor privileged over the inode. We will use this helper both in write operation permission removal such as file_remove_privs() as well as in ownership change operations. Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx> Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/attr.c | 25 +++++++++++++++++++++++++ fs/internal.h | 5 +++++ 2 files changed, 30 insertions(+) --- a/fs/attr.c +++ b/fs/attr.c @@ -20,6 +20,31 @@ #include "internal.h" +/** + * setattr_should_drop_sgid - determine whether the setgid bit needs to be + * removed + * @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(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(inode, inode->i_gid)) + return ATTR_KILL_SGID; + return 0; +} + /* * The logic we want is * --- a/fs/internal.h +++ b/fs/internal.h @@ -197,3 +197,8 @@ int sb_init_dio_done_wq(struct super_blo */ int do_statx(int dfd, const char __user *filename, unsigned flags, unsigned int mask, struct statx __user *buffer); + +/* + * fs/attr.c + */ +int setattr_should_drop_sgid(const struct inode *inode); Patches currently in stable-queue which might be from stable-owner@xxxxxxxxxxxxxxx are queue-5.10/xfs-fallocate-should-call-file_modified.patch queue-5.10/attr-add-setattr_should_drop_sgid.patch queue-5.10/xfs-set-prealloc-flag-in-xfs_alloc_file_space.patch queue-5.10/xfs-purge-dquots-after-inode-walk-fails-during-quotacheck.patch queue-5.10/fs-use-consistent-setgid-checks-in-is_sxid.patch queue-5.10/xfs-remove-xfs_prealloc_sync.patch queue-5.10/attr-add-in_group_or_capable.patch queue-5.10/xfs-don-t-assert-fail-on-perag-references-on-teardown.patch queue-5.10/xfs-don-t-leak-btree-cursor-when-insrec-fails-after-a-split.patch queue-5.10/fs-move-s_isgid-stripping-into-the-vfs_-helpers.patch queue-5.10/xfs-remove-xfs_setattr_time-declaration.patch queue-5.10/fs-move-should_remove_suid.patch queue-5.10/attr-use-consistent-sgid-stripping-checks.patch queue-5.10/fs-add-mode_strip_sgid-helper.patch queue-5.10/xfs-use-setattr_copy-to-set-vfs-inode-attributes.patch