+Cc Thomas Weißschuh <thomas@xxxxxxxx> as this seems quite related to his finding about /proc/self/net: https://lore.kernel.org/lkml/20230624-proc-net-setattr-v1-0-73176812adee@xxxxxxxxxxxxxx/#b On Thu, Jul 13, 2023 at 10:19:04PM +1000, Aleksa Sarai wrote: > Due to an oversight in commit 1b3044e39a89 ("procfs: fix pthread > cross-thread naming if !PR_DUMPABLE") in switching from REG to NOD, > chmod operations on /proc/thread-self/comm were no longer blocked as > they are on almost all other procfs files. > > A very similar situation with /proc/self/environ was used to as a root > exploit a long time ago, but procfs has SB_I_NOEXEC so this is simply a > correctness issue. > > Ref: https://lwn.net/Articles/191954/ > Ref: 6d76fa58b050 ("Don't allow chmod() on the /proc/<pid>/ files") > Fixes: 1b3044e39a89 ("procfs: fix pthread cross-thread naming if !PR_DUMPABLE") > Cc: stable@xxxxxxxxxxxxxxx # v4.7+ > Signed-off-by: Aleksa Sarai <cyphar@xxxxxxxxxx> > --- > fs/proc/base.c | 3 ++- > tools/testing/selftests/nolibc/nolibc-test.c | 4 ++++ > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index 05452c3b9872..7394229816f3 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -3583,7 +3583,8 @@ static int proc_tid_comm_permission(struct mnt_idmap *idmap, > } > > static const struct inode_operations proc_tid_comm_inode_operations = { > - .permission = proc_tid_comm_permission, > + .setattr = proc_setattr, > + .permission = proc_tid_comm_permission, > }; > > /* > diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c > index 486334981e60..08f0969208eb 100644 > --- a/tools/testing/selftests/nolibc/nolibc-test.c > +++ b/tools/testing/selftests/nolibc/nolibc-test.c > @@ -580,6 +580,10 @@ int run_syscall(int min, int max) > CASE_TEST(chmod_net); EXPECT_SYSZR(proc, chmod("/proc/self/net", 0555)); break; > CASE_TEST(chmod_self); EXPECT_SYSER(proc, chmod("/proc/self", 0555), -1, EPERM); break; > CASE_TEST(chown_self); EXPECT_SYSER(proc, chown("/proc/self", 0, 0), -1, EPERM); break; > + CASE_TEST(chmod_self_comm); EXPECT_SYSER(proc, chmod("/proc/self/comm", 0777), -1, EPERM); break; > + CASE_TEST(chmod_tid_comm); EXPECT_SYSER(proc, chmod("/proc/thread-self/comm", 0777), -1, EPERM); break; > + CASE_TEST(chmod_self_environ);EXPECT_SYSER(proc, chmod("/proc/self/environ", 0777), -1, EPERM); break; > + CASE_TEST(chmod_tid_environ); EXPECT_SYSER(proc, chmod("/proc/thread-self/environ", 0777), -1, EPERM); break; > CASE_TEST(chroot_root); EXPECT_SYSZR(euid0, chroot("/")); break; > CASE_TEST(chroot_blah); EXPECT_SYSER(1, chroot("/proc/self/blah"), -1, ENOENT); break; > CASE_TEST(chroot_exe); EXPECT_SYSER(proc, chroot("/proc/self/exe"), -1, ENOTDIR); break; > -- > 2.41.0
