From 36711f9ba818beeee2e5b168cfa8481faf67fcb5 Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Mon, 13 Jun 2016 07:40:54 -0400 Subject: [PATCH] CVE-2016-1583 stack overflow via ecryptfs and /proc (rhbz 1344721 1344722) --- ...d-opening-files-without-mmap-handler.patch | 59 +++++++++++++++++++ kernel.spec | 8 +++ ...-prevent-stacking-filesystems-on-top.patch | 41 +++++++++++++ sched-panic-on-corrupted-stack-end.patch | 36 +++++++++++ 4 files changed, 144 insertions(+) create mode 100644 ecryptfs-forbid-opening-files-without-mmap-handler.patch create mode 100644 proc-prevent-stacking-filesystems-on-top.patch create mode 100644 sched-panic-on-corrupted-stack-end.patch diff --git a/ecryptfs-forbid-opening-files-without-mmap-handler.patch b/ecryptfs-forbid-opening-files-without-mmap-handler.patch new file mode 100644 index 000000000..2d40e68ed --- /dev/null +++ b/ecryptfs-forbid-opening-files-without-mmap-handler.patch @@ -0,0 +1,59 @@ +From 2f36db71009304b3f0b95afacd8eba1f9f046b87 Mon Sep 17 00:00:00 2001 +From: Jann Horn +Date: Wed, 1 Jun 2016 11:55:06 +0200 +Subject: [PATCH] ecryptfs: forbid opening files without mmap handler + +This prevents users from triggering a stack overflow through a recursive +invocation of pagefault handling that involves mapping procfs files into +virtual memory. + +Signed-off-by: Jann Horn +Acked-by: Tyler Hicks +Cc: stable@vger.kernel.org +Signed-off-by: Linus Torvalds +--- + fs/ecryptfs/kthread.c | 13 +++++++++++-- + 1 file changed, 11 insertions(+), 2 deletions(-) + +diff --git a/fs/ecryptfs/kthread.c b/fs/ecryptfs/kthread.c +index 866bb18efefe..e818f5ac7a26 100644 +--- a/fs/ecryptfs/kthread.c ++++ b/fs/ecryptfs/kthread.c +@@ -25,6 +25,7 @@ + #include + #include + #include ++#include + #include "ecryptfs_kernel.h" + + struct ecryptfs_open_req { +@@ -147,7 +148,7 @@ int ecryptfs_privileged_open(struct file **lower_file, + flags |= IS_RDONLY(d_inode(lower_dentry)) ? O_RDONLY : O_RDWR; + (*lower_file) = dentry_open(&req.path, flags, cred); + if (!IS_ERR(*lower_file)) +- goto out; ++ goto have_file; + if ((flags & O_ACCMODE) == O_RDONLY) { + rc = PTR_ERR((*lower_file)); + goto out; +@@ -165,8 +166,16 @@ int ecryptfs_privileged_open(struct file **lower_file, + mutex_unlock(&ecryptfs_kthread_ctl.mux); + wake_up(&ecryptfs_kthread_ctl.wait); + wait_for_completion(&req.done); +- if (IS_ERR(*lower_file)) ++ if (IS_ERR(*lower_file)) { + rc = PTR_ERR(*lower_file); ++ goto out; ++ } ++have_file: ++ if ((*lower_file)->f_op->mmap == NULL) { ++ fput(*lower_file); ++ *lower_file = NULL; ++ rc = -EMEDIUMTYPE; ++ } + out: + return rc; + } +-- +2.5.5 + diff --git a/kernel.spec b/kernel.spec index 4e53f2412..688001131 100644 --- a/kernel.spec +++ b/kernel.spec @@ -628,6 +628,11 @@ Patch721: tipc-fix-an-infoleak-in-tipc_nl_compat_link_dump.patch #CVE-2016-5244 rhbz 1343338 1343337 Patch722: rds-fix-an-infoleak-in-rds_inc_info_copy.txt +#CVE-2016-1583 rhbz 1344721 1344722 +Patch723: proc-prevent-stacking-filesystems-on-top.patch +Patch725: ecryptfs-forbid-opening-files-without-mmap-handler.patch +Patch726: sched-panic-on-corrupted-stack-end.patch + # END OF PATCH DEFINITIONS %endif @@ -2153,6 +2158,9 @@ fi # # %changelog +* Mon Jun 13 2016 Josh Boyer +- CVE-2016-1583 stack overflow via ecryptfs and /proc (rhbz 1344721 1344722) + * Wed Jun 08 2016 Josh Boyer - Linux v4.6.2 diff --git a/proc-prevent-stacking-filesystems-on-top.patch b/proc-prevent-stacking-filesystems-on-top.patch new file mode 100644 index 000000000..178aa3ba6 --- /dev/null +++ b/proc-prevent-stacking-filesystems-on-top.patch @@ -0,0 +1,41 @@ +From e54ad7f1ee263ffa5a2de9c609d58dfa27b21cd9 Mon Sep 17 00:00:00 2001 +From: Jann Horn +Date: Wed, 1 Jun 2016 11:55:05 +0200 +Subject: [PATCH] proc: prevent stacking filesystems on top + +This prevents stacking filesystems (ecryptfs and overlayfs) from using +procfs as lower filesystem. There is too much magic going on inside +procfs, and there is no good reason to stack stuff on top of procfs. + +(For example, procfs does access checks in VFS open handlers, and +ecryptfs by design calls open handlers from a kernel thread that doesn't +drop privileges or so.) + +Signed-off-by: Jann Horn +Cc: stable@vger.kernel.org +Signed-off-by: Linus Torvalds +--- + fs/proc/root.c | 7 +++++++ + 1 file changed, 7 insertions(+) + +diff --git a/fs/proc/root.c b/fs/proc/root.c +index 361ab4ee42fc..ec649c92d270 100644 +--- a/fs/proc/root.c ++++ b/fs/proc/root.c +@@ -121,6 +121,13 @@ static struct dentry *proc_mount(struct file_system_type *fs_type, + if (IS_ERR(sb)) + return ERR_CAST(sb); + ++ /* ++ * procfs isn't actually a stacking filesystem; however, there is ++ * too much magic going on inside it to permit stacking things on ++ * top of it ++ */ ++ sb->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; ++ + if (!proc_parse_options(options, ns)) { + deactivate_locked_super(sb); + return ERR_PTR(-EINVAL); +-- +2.5.5 + diff --git a/sched-panic-on-corrupted-stack-end.patch b/sched-panic-on-corrupted-stack-end.patch new file mode 100644 index 000000000..1d6bbaf3d --- /dev/null +++ b/sched-panic-on-corrupted-stack-end.patch @@ -0,0 +1,36 @@ +From 29d6455178a09e1dc340380c582b13356227e8df Mon Sep 17 00:00:00 2001 +From: Jann Horn +Date: Wed, 1 Jun 2016 11:55:07 +0200 +Subject: [PATCH] sched: panic on corrupted stack end + +Until now, hitting this BUG_ON caused a recursive oops (because oops +handling involves do_exit(), which calls into the scheduler, which in +turn raises an oops), which caused stuff below the stack to be +overwritten until a panic happened (e.g. via an oops in interrupt +context, caused by the overwritten CPU index in the thread_info). + +Just panic directly. + +Signed-off-by: Jann Horn +Signed-off-by: Linus Torvalds +--- + kernel/sched/core.c | 3 ++- + 1 file changed, 2 insertions(+), 1 deletion(-) + +diff --git a/kernel/sched/core.c b/kernel/sched/core.c +index d1f7149f8704..11546a6ed5df 100644 +--- a/kernel/sched/core.c ++++ b/kernel/sched/core.c +@@ -3047,7 +3047,8 @@ static noinline void __schedule_bug(struct task_struct *prev) + static inline void schedule_debug(struct task_struct *prev) + { + #ifdef CONFIG_SCHED_STACK_END_CHECK +- BUG_ON(task_stack_end_corrupted(prev)); ++ if (task_stack_end_corrupted(prev)) ++ panic("corrupted stack end detected inside scheduler\n"); + #endif + + if (unlikely(in_atomic_preempt_off())) { +-- +2.5.5 +