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| author | Aaron Durbin <adurbin@chromium.org> | 2017-05-12 09:55:16 -0500 |
|---|---|---|
| committer | Aaron Durbin <adurbin@chromium.org> | 2017-05-15 19:45:49 +0200 |
| commit | 7ad44eed08b9811d97462b3c990129187f77e2ca (patch) | |
| tree | 67effd79628fabf547a49b05cc95fee6e900d1f3 /util/cbmem | |
| parent | a7092750b2c7856f72016dd0b468f1a1d0585b5a (diff) | |
| download | coreboot-7ad44eed08b9811d97462b3c990129187f77e2ca.tar.xz | |
util/cbmem: mmap underflow on low addresses
There is code to adjust the mapping down if a mmap fails
at a physical address. However, if the address is less
than the page size of the system then the physical offset will
underflow. This can actually cause a kernel panic on when
operating on /dev/mem.
The failing condition happens when the requested mapping at 0
fails in the kernel. The fallback path is taken and page size
is subtracted from 0 making a very large offset. The PAT code
in the kernel fails with a BUG_ON in reserve_memtype() checking
start >= end. The kernel needs to be fixed as well, but this
fallback path is wrong as well.
BUG=b:38211793
Change-Id: I32b0c15b2f1aa43fc57656d5d2d5f0e4e90e94ef
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/19679
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Diffstat (limited to 'util/cbmem')
| -rw-r--r-- | util/cbmem/cbmem.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/util/cbmem/cbmem.c b/util/cbmem/cbmem.c index c1b1caa572..48a1bc963d 100644 --- a/util/cbmem/cbmem.c +++ b/util/cbmem/cbmem.c @@ -165,7 +165,9 @@ static void *map_memory_size(u64 physical, size_t size, uint8_t abort_on_failure v = mmap(NULL, size, PROT_READ, MAP_SHARED, mem_fd, p); - if (v == MAP_FAILED) { + /* Only try growing down when address exceeds page size so that + one doesn't underflow the offset request. */ + if (v == MAP_FAILED && p >= page) { /* The mapped area may have overrun the upper cbmem boundary when trying to * align to the page size. Try growing down instead of up... */ |