| Message ID | 20201007103608.17349-1-cyphar@cyphar.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | openat2: reject RESOLVE_BENEATH|RESOLVE_IN_ROOT | expand |
On Wed, Oct 07, 2020 at 09:36:08PM +1100, Aleksa Sarai wrote: > This was an oversight in the original implementation, as it makes no > sense to specify both scoping flags to the same openat2(2) invocation > (before this patch, the result of such an invocation was equivalent to > RESOLVE_IN_ROOT being ignored). > > This is a userspace-visible ABI change, but the only user of openat2(2) > at the moment is LXC which doesn't specify both flags and so no > userspace programs will break as a result. Indeed! > > Fixes: fddb5d430ad9 ("open: introduce openat2(2) syscall") > Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> > Acked-by: Christian Brauner <christian.brauner@ubuntu.com> > Cc: <stable@vger.kernel.org> # v5.6+ > --- Thanks! This is a good fix imho. Christian
On 10/7/20 4:36 AM, Aleksa Sarai wrote: > This was an oversight in the original implementation, as it makes no > sense to specify both scoping flags to the same openat2(2) invocation > (before this patch, the result of such an invocation was equivalent to > RESOLVE_IN_ROOT being ignored). > > This is a userspace-visible ABI change, but the only user of openat2(2) > at the moment is LXC which doesn't specify both flags and so no > userspace programs will break as a result. > > Cc: <stable@vger.kernel.org> # v5.6+ > Fixes: fddb5d430ad9 ("open: introduce openat2(2) syscall") > Acked-by: Christian Brauner <christian.brauner@ubuntu.com> > Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> > --- > fs/open.c | 4 +++ > tools/testing/selftests/openat2/openat2_test.c | 8 +++++++- You are combining fs change with selftest change. Is there a reason why these two changes are combined? 2 separate patches is better. thanks, -- Shuah
diff --git a/fs/open.c b/fs/open.c index 9af548fb841b..4d7537ae59df 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1010,6 +1010,10 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op) if (how->resolve & ~VALID_RESOLVE_FLAGS) return -EINVAL; + /* Scoping flags are mutually exclusive. */ + if ((how->resolve & RESOLVE_BENEATH) && (how->resolve & RESOLVE_IN_ROOT)) + return -EINVAL; + /* Deal with the mode. */ if (WILL_CREATE(flags)) { if (how->mode & ~S_IALLUGO) diff --git a/tools/testing/selftests/openat2/openat2_test.c b/tools/testing/selftests/openat2/openat2_test.c index b386367c606b..381d874cce99 100644 --- a/tools/testing/selftests/openat2/openat2_test.c +++ b/tools/testing/selftests/openat2/openat2_test.c @@ -155,7 +155,7 @@ struct flag_test { int err; }; -#define NUM_OPENAT2_FLAG_TESTS 23 +#define NUM_OPENAT2_FLAG_TESTS 24 void test_openat2_flags(void) { @@ -210,6 +210,12 @@ void test_openat2_flags(void) .how.flags = O_TMPFILE | O_RDWR, .how.mode = 0x0000A00000000000ULL, .err = -EINVAL }, + /* ->resolve flags must not conflict. */ + { .name = "incompatible resolve flags (BENEATH | IN_ROOT)", + .how.flags = O_RDONLY, + .how.resolve = RESOLVE_BENEATH | RESOLVE_IN_ROOT, + .err = -EINVAL }, + /* ->resolve must only contain RESOLVE_* flags. */ { .name = "invalid how.resolve and O_RDONLY", .how.flags = O_RDONLY,
This was an oversight in the original implementation, as it makes no sense to specify both scoping flags to the same openat2(2) invocation (before this patch, the result of such an invocation was equivalent to RESOLVE_IN_ROOT being ignored). This is a userspace-visible ABI change, but the only user of openat2(2) at the moment is LXC which doesn't specify both flags and so no userspace programs will break as a result. Cc: <stable@vger.kernel.org> # v5.6+ Fixes: fddb5d430ad9 ("open: introduce openat2(2) syscall") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> --- fs/open.c | 4 ++++ tools/testing/selftests/openat2/openat2_test.c | 8 +++++++- 2 files changed, 11 insertions(+), 1 deletion(-)