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Committer:
Ben Hutchings
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Date:
2021-04-29 14:02:58 UTC
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Revision ID:
git-v1:abe5c3477ffa5e91029ef040aede622145dcc777
[klibc] malloc: Fail if block size is out of range for sbrk
sbrk() takes a parameter of type intptr_t. We allow allocating up to
PTRDIFF_MAX (equal to INPTPTR_MAX), and then add a header to that, so
the result fsize can be > INTPTR_MAX. The conversion of fsize to
intptr_t would then result in undefined behaviour (but probably
*lowering* the top of heap). Fail cleanly before that happens.
This is currently a theoretical problem since we actually use mmap()
instead of sbrk() on all architectures.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>