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| author | Theodore Ts'o <tytso@mit.edu> | 2009-09-07 16:21:49 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2009-09-07 16:21:49 -0400 |
| commit | 51e64594919c986f87267b895504322a38ec4fac (patch) | |
| tree | 675d48077dd6c01fda1fea9da41fe589472747cd | |
| parent | 7a9f055f0e7aae18daddc4e5fe9c29babab53b90 (diff) | |
| download | e2fsprogs-51e64594919c986f87267b895504322a38ec4fac.tar.gz | |
libext2fs: Round up the bitmap size when allocating a new bitmap
The x86 BT assembly instructure can overshoot the end of a bit array
when testing a bit at the end of the bit array, even if it never needs
to look at those memory locations. This can cause a spurious
segmentation fault. If we allocate a little extra memory, it avoids
this problem. See:
http://faydoc.tripod.com/cpu/bt.htm
This doesn't happen on Linux, probably because of the glibc's malloc()
function works, but apparently it's a major problem on the *BSD
operating systems.
Addresses-Sourceforge-Bug: #2328708
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
| -rw-r--r-- | lib/ext2fs/gen_bitmap.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/lib/ext2fs/gen_bitmap.c b/lib/ext2fs/gen_bitmap.c index 1f7d2c4c..54a39dcb 100644 --- a/lib/ext2fs/gen_bitmap.c +++ b/lib/ext2fs/gen_bitmap.c @@ -103,6 +103,8 @@ errcode_t ext2fs_make_generic_bitmap(errcode_t magic, ext2_filsys fs, bitmap->description = 0; size = (size_t) (((bitmap->real_end - bitmap->start) / 8) + 1); + /* Round up to allow for the BT x86 instruction */ + size = (size + 7) & ~3; retval = ext2fs_get_mem(size, &bitmap->bitmap); if (retval) { ext2fs_free_mem(&bitmap->description); |