https://github.com/torvalds/linux
Revision f798a1d4f94de9510e060d37b9b47721065a957c authored by Suren Baghdasaryan on 26 February 2022, 03:11:05 UTC, committed by Linus Torvalds on 26 February 2022, 17:51:17 UTC
oom reaping (__oom_reap_task_mm) relies on a 2 way synchronization with exit_mmap. First it relies on the mmap_lock to exclude from unlock path[1], page tables tear down (free_pgtables) and vma destruction. This alone is not sufficient because mm->mmap is never reset. For historical reasons[2] the lock is taken there is also MMF_OOM_SKIP set for oom victims before. The oom reaper only ever looks at oom victims so the whole scheme works properly but process_mrelease can opearate on any task (with fatal signals pending) which doesn't really imply oom victims. That means that the MMF_OOM_SKIP part of the synchronization doesn't work and it can see a task after the whole address space has been demolished and traverse an already released mm->mmap list. This leads to use after free as properly caught up by KASAN report. Fix the issue by reseting mm->mmap so that MMF_OOM_SKIP synchronization is not needed anymore. The MMF_OOM_SKIP is not removed from exit_mmap yet but it acts mostly as an optimization now. [1] 27ae357fa82b ("mm, oom: fix concurrent munlock and oom reaper unmap, v3") [2] 212925802454 ("mm: oom: let oom_reap_task and exit_mmap run concurrently") [mhocko@suse.com: changelog rewrite] Link: https://lore.kernel.org/all/00000000000072ef2c05d7f81950@google.com/ Link: https://lkml.kernel.org/r/20220215201922.1908156-1-surenb@google.com Fixes: 64591e8605d6 ("mm: protect free_pgtables with mmap_lock write lock in exit_mmap") Signed-off-by: Suren Baghdasaryan <surenb@google.com> Reported-by: syzbot+2ccf63a4bd07cf39cab0@syzkaller.appspotmail.com Suggested-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Rik van Riel <riel@surriel.com> Reviewed-by: Yang Shi <shy828301@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Rik van Riel <riel@surriel.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Florian Weimer <fweimer@redhat.com> Cc: Jan Engelhardt <jengelh@inai.de> Cc: Tim Murray <timmurray@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Tip revision: f798a1d4f94de9510e060d37b9b47721065a957c authored by Suren Baghdasaryan on 26 February 2022, 03:11:05 UTC
mm: fix use-after-free bug when mm->mmap is reused after being freed
mm: fix use-after-free bug when mm->mmap is reused after being freed
Tip revision: f798a1d
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kernel | ||
lib | ||
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net | ||
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COPYING | -rw-r--r-- | 496 bytes |
CREDITS | -rw-r--r-- | 98.8 KB |
Kbuild | -rw-r--r-- | 1.3 KB |
Kconfig | -rw-r--r-- | 555 bytes |
MAINTAINERS | -rw-r--r-- | 627.6 KB |
Makefile | -rw-r--r-- | 63.5 KB |
README | -rw-r--r-- | 727 bytes |
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