user/sven/linux.git/fs/proc, branch v3.16.66

coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping

2019-05-02T20:42:04Z

commit 04f5866e41fb70690e28397487d8bd8eea7d712a upstream. The core dumping code has always run without holding the mmap_sem for writing, despite that is the only way to ensure that the entire vma layout will not change from under it. Only using some signal serialization on the processes belonging to the mm is not nearly enough. This was pointed out earlier. For example in Hugh's post from Jul 2017: https://lkml.kernel.org/r/alpine.LSU.2.11.1707191716030.2055@eggly.anvils "Not strictly relevant here, but a related note: I was very surprised to discover, only quite recently, how handle_mm_fault() may be called without down_read(mmap_sem) - when core dumping. That seems a misguided optimization to me, which would also be nice to correct" In particular because the growsdown and growsup can move the vm_start/vm_end the various loops the core dump does around the vma will not be consistent if page faults can happen concurrently. Pretty much all users calling mmget_not_zero()/get_task_mm() and then taking the mmap_sem had the potential to introduce unexpected side effects in the core dumping code. Adding mmap_sem for writing around the ->core_dump invocation is a viable long term fix, but it requires removing all copy user and page faults and to replace them with get_dump_page() for all binary formats which is not suitable as a short term fix. For the time being this solution manually covers the places that can confuse the core dump either by altering the vma layout or the vma flags while it runs. Once ->core_dump runs under mmap_sem for writing the function mmget_still_valid() can be dropped. Allowing mmap_sem protected sections to run in parallel with the coredump provides some minor parallelism advantage to the swapoff code (which seems to be safe enough by never mangling any vma field and can keep doing swapins in parallel to the core dumping) and to some other corner case. In order to facilitate the backporting I added "Fixes: 86039bd3b4e6" however the side effect of this same race condition in /proc/pid/mem should be reproducible since before 2.6.12-rc2 so I couldn't add any other "Fixes:" because there's no hash beyond the git genesis commit. Because find_extend_vma() is the only location outside of the process context that could modify the "mm" structures under mmap_sem for reading, by adding the mmget_still_valid() check to it, all other cases that take the mmap_sem for reading don't need the new check after mmget_not_zero()/get_task_mm(). The expand_stack() in page fault context also doesn't need the new check, because all tasks under core dumping are frozen. Link: http://lkml.kernel.org/r/20190325224949.11068-1-aarcange@redhat.com Fixes: 86039bd3b4e6 ("userfaultfd: add new syscall to provide memory externalization") Signed-off-by: Andrea Arcangeli Reported-by: Jann Horn Suggested-by: Oleg Nesterov Acked-by: Peter Xu Reviewed-by: Mike Rapoport Reviewed-by: Oleg Nesterov Reviewed-by: Jann Horn Acked-by: Jason Gunthorpe Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: - Drop changes in Infiniband and userfaultfd - In clear_refs_write(), use up_read() as we never upgrade to a write lock - Adjust filename, context] Signed-off-by: Ben Hutchings

proc: restrict kernel stack dumps to root

2018-12-16T22:09:37Z

commit f8a00cef17206ecd1b30d3d9f99e10d9fa707aa7 upstream. Currently, you can use /proc/self/task/*/stack to cause a stack walk on a task you control while it is running on another CPU. That means that the stack can change under the stack walker. The stack walker does have guards against going completely off the rails and into random kernel memory, but it can interpret random data from your kernel stack as instruction pointers and stack pointers. This can cause exposure of kernel stack contents to userspace. Restrict the ability to inspect kernel stacks of arbitrary tasks to root in order to prevent a local attacker from exploiting racy stack unwinding to leak kernel task stack contents. See the added comment for a longer rationale. There don't seem to be any users of this userspace API that can't gracefully bail out if reading from the file fails. Therefore, I believe that this change is unlikely to break things. In the case that this patch does end up needing a revert, the next-best solution might be to fake a single-entry stack based on wchan. Link: http://lkml.kernel.org/r/20180927153316.200286-1-jannh@google.com Fixes: 2ec220e27f50 ("proc: add /proc/*/stack") Signed-off-by: Jann Horn Acked-by: Kees Cook Cc: Alexey Dobriyan Cc: Ken Chen Cc: Will Deacon Cc: Laura Abbott Cc: Andy Lutomirski Cc: Catalin Marinas Cc: Josh Poimboeuf Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H . Peter Anvin" Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings

fs/proc: Stop trying to report thread stacks

2018-11-20T18:05:58Z

commit b18cb64ead400c01bf1580eeba330ace51f8087d upstream. This reverts more of: b76437579d13 ("procfs: mark thread stack correctly in proc//maps") ... which was partially reverted by: 65376df58217 ("proc: revert /proc//maps [stack:TID] annotation") Originally, /proc/PID/task/TID/maps was the same as /proc/TID/maps. In current kernels, /proc/PID/maps (or /proc/TID/maps even for threads) shows "[stack]" for VMAs in the mm's stack address range. In contrast, /proc/PID/task/TID/maps uses KSTK_ESP to guess the target thread's stack's VMA. This is racy, probably returns garbage and, on arches with CONFIG_TASK_INFO_IN_THREAD=y, is also crash-prone: KSTK_ESP is not safe to use on tasks that aren't known to be running ordinary process-context kernel code. This patch removes the difference and just shows "[stack]" for VMAs in the mm's stack range. This is IMO much more sensible -- the actual "stack" address really is treated specially by the VM code, and the current thread stack isn't even well-defined for programs that frequently switch stacks on their own. Reported-by: Jann Horn Signed-off-by: Andy Lutomirski Acked-by: Thomas Gleixner Cc: Al Viro Cc: Andrew Morton Cc: Borislav Petkov Cc: Brian Gerst Cc: Johannes Weiner Cc: Kees Cook Cc: Linus Torvalds Cc: Linux API Cc: Peter Zijlstra Cc: Tycho Andersen Link: http://lkml.kernel.org/r/3e678474ec14e0a0ec34c611016753eea2e1b8ba.1475257877.git.luto@kernel.org Signed-off-by: Ingo Molnar [bwh: Backported to 3.16: Squash in the earlier commits 58cb65487e92 "proc/maps: make vm_is_stack() logic namespace-friendly" and 65376df58217 "proc: revert /proc//maps [stack:TID] annotation", which would introduce build failures if applied separately.] Signed-off-by: Ben Hutchings

mm: /proc/pid/pagemap: hide swap entries from unprivileged users

2018-11-20T18:05:11Z

commit ab6ecf247a9321e3180e021a6a60164dee53ab2e upstream. In commit ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace"), the /proc/PID/pagemap is restricted to be readable only by CAP_SYS_ADMIN to address some security issue. In commit 1c90308e7a77 ("pagemap: hide physical addresses from non-privileged users"), the restriction is relieved to make /proc/PID/pagemap readable, but hide the physical addresses for non-privileged users. But the swap entries are readable for non-privileged users too. This has some security issues. For example, for page under migrating, the swap entry has physical address information. So, in this patch, the swap entries are hided for non-privileged users too. Link: http://lkml.kernel.org/r/20180508012745.7238-1-ying.huang@intel.com Fixes: 1c90308e7a77 ("pagemap: hide physical addresses from non-privileged users") Signed-off-by: "Huang, Ying" Suggested-by: Kirill A. Shutemov Reviewed-by: Naoya Horiguchi Reviewed-by: Konstantin Khlebnikov Acked-by: Michal Hocko Cc: Konstantin Khlebnikov Cc: Andrei Vagin Cc: Jerome Glisse Cc: Daniel Colascione Cc: Zi Yan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: - Only PTEs can be swap entries - Adjust context] Signed-off-by: Ben Hutchings

pagemap: hide physical addresses from non-privileged users

2018-11-20T18:05:11Z

commit 1c90308e7a77af6742a97d1021cca923b23b7f0d upstream. This patch makes pagemap readable for normal users and hides physical addresses from them. For some use-cases PFN isn't required at all. See http://lkml.kernel.org/r/1425935472-17949-1-git-send-email-kirill@shutemov.name Fixes: ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace") Signed-off-by: Konstantin Khlebnikov Cc: Naoya Horiguchi Reviewed-by: Mark Williamson Tested-by: Mark Williamson Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: - Add the same check in the places where we look up a PFN - Adjust context] Signed-off-by: Ben Hutchings

fs/proc/proc_sysctl.c: fix potential page fault while unregistering sysctl table

2018-10-21T07:45:21Z

commit a0b0d1c345d0317efe594df268feb5ccc99f651e upstream. proc_sys_link_fill_cache() does not take currently unregistering sysctl tables into account, which might result into a page fault in sysctl_follow_link() - add a check to fix it. This bug has been present since v3.4. Link: http://lkml.kernel.org/r/20180228013506.4915-1-danilokrummrich@dk-develop.de Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between sysctl_table_sets") Signed-off-by: Danilo Krummrich Acked-by: Kees Cook Reviewed-by: Andrew Morton Cc: "Luis R . Rodriguez" Cc: "Eric W. Biederman" Cc: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings

proc: drop handling non-linear mappings

2018-10-03T03:09:51Z

commit 1da4b35b001481df99a6dcab12d5d39a876f7056 upstream. We have to handle non-linear mappings for /proc/PID/{smaps,clear_refs} which is unused now. Let's drop it. Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: - Deleted code is slightly different - Adjust context] Signed-off-by: Ben Hutchings

proc: Use underscores for SSBD in 'status'

2018-10-03T03:09:44Z

commit e96f46ee8587607a828f783daa6eb5b44d25004d upstream. The style for the 'status' file is CamelCase or this. _. Fixes: fae1fa0fc ("proc: Provide details on speculation flaw mitigations") Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Thomas Gleixner [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings

prctl: Add force disable speculation

2018-10-03T03:09:42Z

commit 356e4bfff2c5489e016fdb925adbf12a1e3950ee upstream. For certain use cases it is desired to enforce mitigations so they cannot be undone afterwards. That's important for loader stubs which want to prevent a child from disabling the mitigation again. Will also be used for seccomp(). The extra state preserving of the prctl state for SSB is a preparatory step for EBPF dymanic speculation control. Signed-off-by: Thomas Gleixner [bwh: Backported to 3.16: adjust filename, context] Signed-off-by: Ben Hutchings

proc: Provide details on speculation flaw mitigations

2018-10-03T03:09:42Z

commit fae1fa0fc6cca8beee3ab8ed71d54f9a78fa3f64 upstream. As done with seccomp and no_new_privs, also show speculation flaw mitigation state in /proc/$pid/status. Signed-off-by: Kees Cook Signed-off-by: Thomas Gleixner Signed-off-by: Ben Hutchings