On Tue, Jan 03, 2023 at 04:28:20PM +0100, Christian Brauner wrote:
> Over mutiple kernel releases we have reworked setgid inheritance
> significantly due to long-standing security issues, security issues that
> were reintroduced after they were fixed, and the subtle and difficult
> inheritance rules that plagued individual filesystems. We have lifted
> setgid inheritance into the VFS proper in earlier patches. Starting with
> kernel v6.2 we have made setgid inheritance consistent between the write
> and setattr (ch{mod,own}) paths.
>
> The gist of the requirement is that in order to inherit the setgid bit
> the user needs to be in the group of the file or have CAP_FSETID in
> their user namespace. Otherwise the setgid bit will be dropped
> irregardless of the file's executability. Change the tests accordingly
> and annotate them with the commits that changed the behavior.
>
> Note, that only with v6.2 setgid inheritance works correctly for
> overlayfs in the write path. Before this the setgid bit was always
> retained.
>
> Link: https://lore.kernel.org/linux-ext4/CAOQ4uxhmCgyorYVtD6=n=khqwUc=MPbZs+y=sqt09XbGoNm_tA@xxxxxxxxxxxxxx
> Link: https://lore.kernel.org/linux-fsdevel/20221212112053.99208-1-brauner@xxxxxxxxxx
> Link: https://lore.kernel.org/linux-fsdevel/20221122142010.zchf2jz2oymx55qi@wittgenstein
> Cc: Amir Goldstein <amir73il@xxxxxxxxx>
> Cc: Zorro Lang <zlang@xxxxxxxxxx>
> Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
> ---
> tests/generic/673 | 12 +++++++++---
> tests/generic/673.out | 8 ++++----
> tests/generic/683 | 11 ++++++++---
> tests/generic/683.out | 8 ++++----
> tests/generic/684 | 11 ++++++++---
> tests/generic/684.out | 8 ++++----
> tests/generic/685 | 11 ++++++++---
> tests/generic/685.out | 8 ++++----
> 8 files changed, 49 insertions(+), 28 deletions(-)
>
> diff --git a/tests/generic/673 b/tests/generic/673
> index 6d1f49ea..1d8e4184 100755
> --- a/tests/generic/673
> +++ b/tests/generic/673
> @@ -23,6 +23,12 @@ _require_scratch_reflink
> _scratch_mkfs >> $seqres.full
> _scratch_mount
> _require_congruent_file_oplen $SCRATCH_MNT 1048576
> +
> +# Due to multiple security issues and potential for subtle bugs around setgid
> +# inheritance the rules in the write and chmod/chown paths have been made
> +# consistent and are enforced by the VFS since kernel 6.2.
> +_fixed_in_kernel_version "v6.2"
Uh... will this new behavior get ported to the LTS kernels too, or are
we simply changing the kernel behavior here?
Also, this patch does correct the new test failures that I saw as soon
as I pulled 6.2-rc1, but it doesn't fix the finsert and fcollapse tests:
diff -u /tmp/fstests/tests/generic/686.out /var/tmp/fstests/generic/686.out.bad
--- /tmp/fstests/tests/generic/686.out 2022-05-17 17:22:17.998867741 -0700
+++ /var/tmp/fstests/generic/686.out.bad 2023-01-03 09:44:34.316697629 -0800
@@ -33,7 +33,7 @@
Test 9 - qa_user, non-exec file finsert, only sgid
2666 -rw-rwSrw- TEST_DIR/686/a
-2666 -rw-rwSrw- TEST_DIR/686/a
+666 -rw-rw-rw- TEST_DIR/686/a
Test 10 - qa_user, group-exec file finsert, only sgid
2676 -rw-rwsrw- TEST_DIR/686/a
@@ -41,7 +41,7 @@
Test 11 - qa_user, user-exec file finsert, only sgid
2766 -rwxrwSrw- TEST_DIR/686/a
-2766 -rwxrwSrw- TEST_DIR/686/a
+766 -rwxrw-rw- TEST_DIR/686/a
Test 12 - qa_user, all-exec file finsert, only sgid
2777 -rwxrwsrwx TEST_DIR/686/a
[4]alder-mtr00(mtr_x86_64):~(1)> diff -u /tmp/fstests/tests/generic/687.out /var/tmp/fstests/generic/687.out.bad
--- /tmp/fstests/tests/generic/687.out 2022-05-17 17:22:17.998867741 -0700
+++ /var/tmp/fstests/generic/687.out.bad 2023-01-03 09:44:37.232632839 -0800
@@ -33,7 +33,7 @@
Test 9 - qa_user, non-exec file fcollapse, only sgid
2666 -rw-rwSrw- TEST_DIR/687/a
-2666 -rw-rwSrw- TEST_DIR/687/a
+666 -rw-rw-rw- TEST_DIR/687/a
Test 10 - qa_user, group-exec file fcollapse, only sgid
2676 -rw-rwsrw- TEST_DIR/687/a
@@ -41,7 +41,7 @@
Test 11 - qa_user, user-exec file fcollapse, only sgid
2766 -rwxrwSrw- TEST_DIR/687/a
-2766 -rwxrwSrw- TEST_DIR/687/a
+766 -rwxrw-rw- TEST_DIR/687/a
Test 12 - qa_user, all-exec file fcollapse, only sgid
2777 -rwxrwsrwx TEST_DIR/687/a
--D
> +
> chmod a+rw $SCRATCH_MNT/
>
> setup_testfile() {
> @@ -102,8 +108,8 @@ setup_testfile
> chmod a+rwxs $SCRATCH_MNT/a
> commit_and_check
>
> -#Commit to a non-exec file by an unprivileged user leaves sgid.
> -echo "Test 9 - qa_user, non-exec file, only sgid"
> +# Commit to a non-exec file by an unprivileged user clears sgid.
> +echo "Test 9 - qa_user, non-exec file"
> setup_testfile
> chmod a+rw,g+rws $SCRATCH_MNT/a
> commit_and_check "$qa_user"
> @@ -115,7 +121,7 @@ chmod a+rw,g+rwxs $SCRATCH_MNT/a
> commit_and_check "$qa_user"
>
> #Commit to a user-exec file by an unprivileged user clears sgid
> -echo "Test 11 - qa_user, user-exec file, only sgid"
> +echo "Test 11 - qa_user, user-exec file"
> setup_testfile
> chmod a+rw,u+x,g+rws $SCRATCH_MNT/a
> commit_and_check "$qa_user"
> diff --git a/tests/generic/673.out b/tests/generic/673.out
> index 0817857d..54e04232 100644
> --- a/tests/generic/673.out
> +++ b/tests/generic/673.out
> @@ -47,11 +47,11 @@ Test 8 - root, all-exec file
> 3784de23efab7a2074c9ec66901e39e5 SCRATCH_MNT/a
> 6777 -rwsrwsrwx SCRATCH_MNT/a
>
> -Test 9 - qa_user, non-exec file, only sgid
> +Test 9 - qa_user, non-exec file
> 310f146ce52077fcd3308dcbe7632bb2 SCRATCH_MNT/a
> 2666 -rw-rwSrw- SCRATCH_MNT/a
> 3784de23efab7a2074c9ec66901e39e5 SCRATCH_MNT/a
> -2666 -rw-rwSrw- SCRATCH_MNT/a
> +666 -rw-rw-rw- SCRATCH_MNT/a
>
> Test 10 - qa_user, group-exec file, only sgid
> 310f146ce52077fcd3308dcbe7632bb2 SCRATCH_MNT/a
> @@ -59,11 +59,11 @@ Test 10 - qa_user, group-exec file, only sgid
> 3784de23efab7a2074c9ec66901e39e5 SCRATCH_MNT/a
> 676 -rw-rwxrw- SCRATCH_MNT/a
>
> -Test 11 - qa_user, user-exec file, only sgid
> +Test 11 - qa_user, user-exec file
> 310f146ce52077fcd3308dcbe7632bb2 SCRATCH_MNT/a
> 2766 -rwxrwSrw- SCRATCH_MNT/a
> 3784de23efab7a2074c9ec66901e39e5 SCRATCH_MNT/a
> -2766 -rwxrwSrw- SCRATCH_MNT/a
> +766 -rwxrw-rw- SCRATCH_MNT/a
>
> Test 12 - qa_user, all-exec file, only sgid
> 310f146ce52077fcd3308dcbe7632bb2 SCRATCH_MNT/a
> diff --git a/tests/generic/683 b/tests/generic/683
> index eea8d21b..74b72e5b 100755
> --- a/tests/generic/683
> +++ b/tests/generic/683
> @@ -30,6 +30,11 @@ verb=falloc
> _require_xfs_io_command $verb
> _require_congruent_file_oplen $TEST_DIR 65536
>
> +# Due to multiple security issues and potential for subtle bugs around setgid
> +# inheritance the rules in the write and chmod/chown paths have been made
> +# consistent and are enforced by the VFS since kernel 6.2.
> +_fixed_in_kernel_version "v6.2"
> +
> junk_dir=$TEST_DIR/$seq
> junk_file=$junk_dir/a
> mkdir -p $junk_dir/
> @@ -110,8 +115,8 @@ setup_testfile
> chmod a+rwxs $junk_file
> commit_and_check "" "$verb" 64k 64k
>
> -# Commit to a non-exec file by an unprivileged user leaves sgid.
> -echo "Test 9 - qa_user, non-exec file $verb, only sgid"
> +# Commit to a non-exec file by an unprivileged user clears sgid.
> +echo "Test 9 - qa_user, non-exec file $verb"
> setup_testfile
> chmod a+rw,g+rws $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
> @@ -123,7 +128,7 @@ chmod a+rw,g+rwxs $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
>
> # Commit to a user-exec file by an unprivileged user clears sgid
> -echo "Test 11 - qa_user, user-exec file $verb, only sgid"
> +echo "Test 11 - qa_user, user-exec file $verb"
> setup_testfile
> chmod a+rw,u+x,g+rws $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
> diff --git a/tests/generic/683.out b/tests/generic/683.out
> index ca29f6e6..a7e04e4a 100644
> --- a/tests/generic/683.out
> +++ b/tests/generic/683.out
> @@ -31,17 +31,17 @@ Test 8 - root, all-exec file falloc
> 6777 -rwsrwsrwx TEST_DIR/683/a
> 6777 -rwsrwsrwx TEST_DIR/683/a
>
> -Test 9 - qa_user, non-exec file falloc, only sgid
> -2666 -rw-rwSrw- TEST_DIR/683/a
> +Test 9 - qa_user, non-exec file falloc
> 2666 -rw-rwSrw- TEST_DIR/683/a
> +666 -rw-rw-rw- TEST_DIR/683/a
>
> Test 10 - qa_user, group-exec file falloc, only sgid
> 2676 -rw-rwsrw- TEST_DIR/683/a
> 676 -rw-rwxrw- TEST_DIR/683/a
>
> -Test 11 - qa_user, user-exec file falloc, only sgid
> -2766 -rwxrwSrw- TEST_DIR/683/a
> +Test 11 - qa_user, user-exec file falloc
> 2766 -rwxrwSrw- TEST_DIR/683/a
> +766 -rwxrw-rw- TEST_DIR/683/a
>
> Test 12 - qa_user, all-exec file falloc, only sgid
> 2777 -rwxrwsrwx TEST_DIR/683/a
> diff --git a/tests/generic/684 b/tests/generic/684
> index 541dbeb4..6fad7f75 100755
> --- a/tests/generic/684
> +++ b/tests/generic/684
> @@ -30,6 +30,11 @@ verb=fpunch
> _require_xfs_io_command $verb
> _require_congruent_file_oplen $TEST_DIR 65536
>
> +# Due to multiple security issues and potential for subtle bugs around setgid
> +# inheritance the rules in the write and chmod/chown paths have been made
> +# consistent and are enforced by the VFS since kernel 6.2.
> +_fixed_in_kernel_version "v6.2"
> +
> junk_dir=$TEST_DIR/$seq
> junk_file=$junk_dir/a
> mkdir -p $junk_dir/
> @@ -110,8 +115,8 @@ setup_testfile
> chmod a+rwxs $junk_file
> commit_and_check "" "$verb" 64k 64k
>
> -# Commit to a non-exec file by an unprivileged user leaves sgid.
> -echo "Test 9 - qa_user, non-exec file $verb, only sgid"
> +# Commit to a non-exec file by an unprivileged user clears sgid.
> +echo "Test 9 - qa_user, non-exec file $verb"
> setup_testfile
> chmod a+rw,g+rws $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
> @@ -123,7 +128,7 @@ chmod a+rw,g+rwxs $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
>
> # Commit to a user-exec file by an unprivileged user clears sgid
> -echo "Test 11 - qa_user, user-exec file $verb, only sgid"
> +echo "Test 11 - qa_user, user-exec file $verb"
> setup_testfile
> chmod a+rw,u+x,g+rws $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
> diff --git a/tests/generic/684.out b/tests/generic/684.out
> index 2e084ced..5c803cd4 100644
> --- a/tests/generic/684.out
> +++ b/tests/generic/684.out
> @@ -31,17 +31,17 @@ Test 8 - root, all-exec file fpunch
> 6777 -rwsrwsrwx TEST_DIR/684/a
> 6777 -rwsrwsrwx TEST_DIR/684/a
>
> -Test 9 - qa_user, non-exec file fpunch, only sgid
> -2666 -rw-rwSrw- TEST_DIR/684/a
> +Test 9 - qa_user, non-exec file fpunch
> 2666 -rw-rwSrw- TEST_DIR/684/a
> +666 -rw-rw-rw- TEST_DIR/684/a
>
> Test 10 - qa_user, group-exec file fpunch, only sgid
> 2676 -rw-rwsrw- TEST_DIR/684/a
> 676 -rw-rwxrw- TEST_DIR/684/a
>
> -Test 11 - qa_user, user-exec file fpunch, only sgid
> -2766 -rwxrwSrw- TEST_DIR/684/a
> +Test 11 - qa_user, user-exec file fpunch
> 2766 -rwxrwSrw- TEST_DIR/684/a
> +766 -rwxrw-rw- TEST_DIR/684/a
>
> Test 12 - qa_user, all-exec file fpunch, only sgid
> 2777 -rwxrwsrwx TEST_DIR/684/a
> diff --git a/tests/generic/685 b/tests/generic/685
> index 29eca1a8..56be0a0c 100755
> --- a/tests/generic/685
> +++ b/tests/generic/685
> @@ -30,6 +30,11 @@ verb=fzero
> _require_xfs_io_command $verb
> _require_congruent_file_oplen $TEST_DIR 65536
>
> +# Due to multiple security issues and potential for subtle bugs around setgid
> +# inheritance the rules in the write and chmod/chown paths have been made
> +# consistent and are enforced by the VFS since kernel 6.2.
> +_fixed_in_kernel_version "v6.2"
> +
> junk_dir=$TEST_DIR/$seq
> junk_file=$junk_dir/a
> mkdir -p $junk_dir/
> @@ -110,8 +115,8 @@ setup_testfile
> chmod a+rwxs $junk_file
> commit_and_check "" "$verb" 64k 64k
>
> -# Commit to a non-exec file by an unprivileged user leaves sgid.
> -echo "Test 9 - qa_user, non-exec file $verb, only sgid"
> +# Commit to a non-exec file by an unprivileged user clears sgid.
> +echo "Test 9 - qa_user, non-exec file $verb"
> setup_testfile
> chmod a+rw,g+rws $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
> @@ -123,7 +128,7 @@ chmod a+rw,g+rwxs $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
>
> # Commit to a user-exec file by an unprivileged user clears sgid
> -echo "Test 11 - qa_user, user-exec file $verb, only sgid"
> +echo "Test 11 - qa_user, user-exec file $verb"
> setup_testfile
> chmod a+rw,u+x,g+rws $junk_file
> commit_and_check "$qa_user" "$verb" 64k 64k
> diff --git a/tests/generic/685.out b/tests/generic/685.out
> index e611da3e..788457ba 100644
> --- a/tests/generic/685.out
> +++ b/tests/generic/685.out
> @@ -31,17 +31,17 @@ Test 8 - root, all-exec file fzero
> 6777 -rwsrwsrwx TEST_DIR/685/a
> 6777 -rwsrwsrwx TEST_DIR/685/a
>
> -Test 9 - qa_user, non-exec file fzero, only sgid
> -2666 -rw-rwSrw- TEST_DIR/685/a
> +Test 9 - qa_user, non-exec file fzero
> 2666 -rw-rwSrw- TEST_DIR/685/a
> +666 -rw-rw-rw- TEST_DIR/685/a
>
> Test 10 - qa_user, group-exec file fzero, only sgid
> 2676 -rw-rwsrw- TEST_DIR/685/a
> 676 -rw-rwxrw- TEST_DIR/685/a
>
> -Test 11 - qa_user, user-exec file fzero, only sgid
> -2766 -rwxrwSrw- TEST_DIR/685/a
> +Test 11 - qa_user, user-exec file fzero
> 2766 -rwxrwSrw- TEST_DIR/685/a
> +766 -rwxrw-rw- TEST_DIR/685/a
>
> Test 12 - qa_user, all-exec file fzero, only sgid
> 2777 -rwxrwsrwx TEST_DIR/685/a
>
> ---
> base-commit: fbd489798b31e32f0eaefcd754326a06aa5b166f
> change-id: 20230103-fstests-setgid-v6-2-4ce5852d11e2
>
> Best regards,
> --
> Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
