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Subject[PATCH v2 0/3] kmemleak: Fix false positive with special scan
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Hi,

There is a false positive case that a pointer is calculated by other
methods than the usual container_of macro. "kmemleak_ignore" can cover
such a false positive, but it would loose the advantage of memory leak
detection. This patch allows kmemleak to work with such false
positives by introducing a new special memory block with a specified
calculation formula. A client module can register its area with a
conversion function, with which function kmemleak scan could calculate
a correct pointer.

For this version 2, to avoid client kernel module being unloaded
before unregistering special conversion, module reference count is
used. This was pointed by Phil Carmody.

A typical use case could be the IOMMU pagetable allocation which
stores pointers to the second level of page tables with some
conversion, for example, a physical address with attribution
bits. Right now I don't have other use cases but I hope that there
could be some that this special scan works with.

Test:

# echo scan > kmemleak
# modprobe kmemleak-special-test
[ 1328.260162] Stored 1024@dfc5ac00 -> 9fc5ac01
[ 1328.264984] Stored 1024@dfc5b800 -> 9fc5b801
[ 1328.269500] Stored 1024@dfc5b400 -> 9fc5b401
[ 1328.273895] Stored 1024@dfc5b000 -> 9fc5b001
[ 1328.278381] Stored 1024@deb9bc00 -> 9eb9bc01
[ 1328.282714] Stored 1024@deea6c00 -> 9eea6c01
[ 1328.287139] Stored 1024@deea7c00 -> 9eea7c01
[ 1328.291473] Stored 1024@deea7800 -> 9eea7801
# echo scan > kmemleak
[ 1344.062591] kmemleak: 8 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
# rmmod kmemleak-special-test
# echo scan > kmemleak
# modprobe kmemleak-special-test timeout=60
[ 71.758850] Stored 1024@dfc5b000 -> 9fc5b001
[ 71.763702] Stored 1024@dfc5b400 -> 9fc5b401
[ 71.768066] Stored 1024@dfc5b800 -> 9fc5b801
[ 71.772583] Stored 1024@dfc5bc00 -> 9fc5bc01
[ 71.776977] Stored 1024@deea6000 -> 9eea6001
[ 71.781341] Stored 1024@deea6400 -> 9eea6401
[ 71.785736] Stored 1024@deea6800 -> 9eea6801
[ 71.790069] Stored 1024@deea6c00 -> 9eea6c01
[ 71.794433] kmemleak_special_init: Registered special scan: bf000360
# echo scan > kmemleak
[ 79.588836] custom_conversion: Converted 9fc5b001 -> dfc5b000
[ 79.594696] custom_conversion: Converted 9fc5b401 -> dfc5b400
[ 79.600494] custom_conversion: Converted 9fc5b801 -> dfc5b800
[ 79.606292] custom_conversion: Converted 9fc5bc01 -> dfc5bc00
[ 79.612060] custom_conversion: Converted 9eea6001 -> deea6000
[ 79.617889] custom_conversion: Converted 9eea6401 -> deea6400
[ 79.623687] custom_conversion: Converted 9eea6801 -> deea6800
[ 79.629486] custom_conversion: Converted 9eea6c01 -> deea6c00
# rmmod kmemleak-special-test
rmmod: cannot unload 'kmemleak_special_test': Resource temporarily unavailable
# lsmod kmemleak-special-test
Module Size Used by Not tainted
kmemleak_special_test 1467 1
# [ 131.800354] no_special_func: Unregistered special scan bf000360
# lsmod kmemleak-special-test
Module Size Used by Not tainted
kmemleak_special_test 1467 0
# rmmod kmemleak-special-test

Hiroshi DOYU (3):
kmemleak: Fix false positives with special scan
kmemleak: Add special scan test case
omap iommu: kmemleak: Fix false positive with special scan

arch/arm/plat-omap/iommu.c | 19 +++++++
include/linux/kmemleak.h | 5 ++
mm/Makefile | 2 +-
mm/kmemleak-special-test.c | 94 ++++++++++++++++++++++++++++++++++++
mm/kmemleak.c | 114 ++++++++++++++++++++++++++++++++++++++++++-
5 files changed, 230 insertions(+), 4 deletions(-)
create mode 100644 mm/kmemleak-special-test.c


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