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authorChristian Brauner <brauner@kernel.org>2022-10-17 17:06:34 +0200
committerChristian Brauner (Microsoft) <brauner@kernel.org>2022-10-18 10:09:43 +0200
commit11c2a8700cdcabf9b639b7204a1e38e2a0b6798e (patch)
treef98a38095132d6d55b9f718ad07d3a3824998bdd /fs/inode.c
parent9abf2313adc1ca1b6180c508c25f22f9395cc780 (diff)
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attr: add in_group_or_capable()
In setattr_{copy,prepare}() we need to perform the same permission checks to determine whether we need to drop the setgid bit or not. Instead of open-coding it twice add a simple helper the encapsulates the logic. We will reuse this helpers to make dropping the setgid bit during write operations more consistent in a follow up patch. Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Diffstat (limited to 'fs/inode.c')
-rw-r--r--fs/inode.c28
1 files changed, 24 insertions, 4 deletions
diff --git a/fs/inode.c b/fs/inode.c
index b608528efd3a..55299b710c45 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2488,6 +2488,28 @@ 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
@@ -2508,11 +2530,9 @@ 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);