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authorJohn Stultz <john.stultz@linaro.org>2018-07-31 10:17:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-01 10:08:57 -0700
commit44960f2a7b63e224b1091b3e1d6f60e0cdf4be0c (patch)
tree2742343319f9f6da22efc457c5a265394a87f4ba
parentebad825cdd4e6b327eaf0dd72439408957049cea (diff)
download96b-common-44960f2a7b63e224b1091b3e1d6f60e0cdf4be0c.tar.gz
staging: ashmem: Fix SIGBUS crash when traversing mmaped ashmem pages
Amit Pundir and Youling in parallel reported crashes with recent mainline kernels running Android: F DEBUG : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** F DEBUG : Build fingerprint: 'Android/db410c32_only/db410c32_only:Q/OC-MR1/102:userdebug/test-key F DEBUG : Revision: '0' F DEBUG : ABI: 'arm' F DEBUG : pid: 2261, tid: 2261, name: zygote >>> zygote <<< F DEBUG : signal 7 (SIGBUS), code 2 (BUS_ADRERR), fault addr 0xec00008 ... <snip> ... F DEBUG : backtrace: F DEBUG : #00 pc 00001c04 /system/lib/libc.so (memset+48) F DEBUG : #01 pc 0010c513 /system/lib/libart.so (create_mspace_with_base+82) F DEBUG : #02 pc 0015c601 /system/lib/libart.so (art::gc::space::DlMallocSpace::CreateMspace(void*, unsigned int, unsigned int)+40) F DEBUG : #03 pc 0015c3ed /system/lib/libart.so (art::gc::space::DlMallocSpace::CreateFromMemMap(art::MemMap*, std::__1::basic_string<char, std::__ 1::char_traits<char>, std::__1::allocator<char>> const&, unsigned int, unsigned int, unsigned int, unsigned int, bool)+36) ... This was bisected back to commit bfd40eaff5ab ("mm: fix vma_is_anonymous() false-positives"). create_mspace_with_base() in the trace above, utilizes ashmem, and with ashmem, for shared mappings we use shmem_zero_setup(), which sets the vma->vm_ops to &shmem_vm_ops. But for private ashmem mappings nothing sets the vma->vm_ops. Looking at the problematic patch, it seems to add a requirement that one call vma_set_anonymous() on a vma, otherwise the dummy_vm_ops will be used. Using the dummy_vm_ops seem to triggger SIGBUS when traversing unmapped pages. Thus, this patch adds a call to vma_set_anonymous() for ashmem private mappings and seems to avoid the reported problem. Fixes: bfd40eaff5ab ("mm: fix vma_is_anonymous() false-positives") Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Joel Fernandes <joelaf@google.com> Cc: Colin Cross <ccross@google.com> Cc: Matthew Wilcox <willy@infradead.org> Reported-by: Amit Pundir <amit.pundir@linaro.org> Reported-by: Youling 257 <youling257@gmail.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/staging/android/ashmem.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
index a1a0025b59e0..d5d33e12e952 100644
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -402,6 +402,8 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
fput(asma->file);
goto out;
}
+ } else {
+ vma_set_anonymous(vma);
}
if (vma->vm_file)