48 lines
1.7 KiB
Diff
48 lines
1.7 KiB
Diff
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From 0fa3ecd87848c9c93c2c828ef4c3a8ca36ce46c7 Mon Sep 17 00:00:00 2001
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From: Linus Torvalds <torvalds@linux-foundation.org>
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Date: Tue, 3 Jul 2018 17:10:19 -0700
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Subject: [PATCH] Fix up non-directory creation in SGID directories
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sgid directories have special semantics, making newly created files in
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the directory belong to the group of the directory, and newly created
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subdirectories will also become sgid. This is historically used for
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group-shared directories.
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But group directories writable by non-group members should not imply
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that such non-group members can magically join the group, so make sure
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to clear the sgid bit on non-directories for non-members (but remember
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that sgid without group execute means "mandatory locking", just to
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confuse things even more).
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Reported-by: Jann Horn <jannh@google.com>
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Cc: Andy Lutomirski <luto@kernel.org>
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Cc: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Jeremy Cline <jcline@redhat.com>
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---
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fs/inode.c | 6 ++++++
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1 file changed, 6 insertions(+)
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diff --git a/fs/inode.c b/fs/inode.c
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index 2c300e981796..8c86c809ca17 100644
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--- a/fs/inode.c
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+++ b/fs/inode.c
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@@ -1999,8 +1999,14 @@ void inode_init_owner(struct inode *inode, const struct inode *dir,
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inode->i_uid = current_fsuid();
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if (dir && dir->i_mode & S_ISGID) {
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inode->i_gid = dir->i_gid;
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+
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+ /* Directories are special, and always inherit S_ISGID */
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if (S_ISDIR(mode))
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mode |= S_ISGID;
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+ else if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP) &&
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+ !in_group_p(inode->i_gid) &&
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+ !capable_wrt_inode_uidgid(dir, CAP_FSETID))
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+ mode &= ~S_ISGID;
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} else
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inode->i_gid = current_fsgid();
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inode->i_mode = mode;
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--
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2.17.1
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