diff options
author | Jan Kara <jack@suse.cz> | 2016-09-19 18:39:09 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-05-08 08:44:10 +0300 |
commit | d8333c045f045385a914013a220cd1ed54c88d48 (patch) | |
tree | 6f3354eeb66b4277f03d695b1c88d1d2f091f6c6 /fs/posix_acl.c | |
parent | 5a7b3b1ec16b6bfa57752d37292988e64fcdd172 (diff) | |
download | linux-d8333c045f045385a914013a220cd1ed54c88d48.tar.xz |
posix_acl: Clear SGID bit when setting file permissions
commit 073931017b49d9458aa351605b43a7e34598caef upstream.
When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok(). Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2). Fix that.
References: CVE-2016-7097
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/posix_acl.c')
-rw-r--r-- | fs/posix_acl.c | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/fs/posix_acl.c b/fs/posix_acl.c index 3de7c223c963..38c91932eb52 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -594,6 +594,37 @@ no_acl: } EXPORT_SYMBOL_GPL(posix_acl_create); +/** + * posix_acl_update_mode - update mode in set_acl + * + * Update the file mode when setting an ACL: compute the new file permission + * bits based on the ACL. In addition, if the ACL is equivalent to the new + * file mode, set *acl to NULL to indicate that no ACL should be set. + * + * As with chmod, clear the setgit bit if the caller is not in the owning group + * or capable of CAP_FSETID (see inode_change_ok). + * + * Called from set_acl inode operations. + */ +int posix_acl_update_mode(struct inode *inode, umode_t *mode_p, + struct posix_acl **acl) +{ + umode_t mode = inode->i_mode; + int error; + + error = posix_acl_equiv_mode(*acl, &mode); + if (error < 0) + return error; + if (error == 0) + *acl = NULL; + if (!in_group_p(inode->i_gid) && + !capable_wrt_inode_uidgid(inode, CAP_FSETID)) + mode &= ~S_ISGID; + *mode_p = mode; + return 0; +} +EXPORT_SYMBOL(posix_acl_update_mode); + /* * Fix up the uids and gids in posix acl extended attributes in place. */ |