linux-user/mmap.c: fix integer underflow in target_mremap
Fixes: https://bugs.launchpad.net/bugs/1876373 This code path in mmap occurs when a page size is decreased with mremap. When a section of pages is shrunk, qemu calls mmap_reserve on the pages that were released. However, it has the diff operation reversed, subtracting the larger old_size from the smaller new_size. Instead, it should be subtracting the smaller new_size from the larger old_size. You can also see in the previous line of the change that this mmap_reserve call only occurs when old_size > new_size. Bug: https://bugs.launchpad.net/qemu/+bug/1876373 Signed-off-by: Jonathan Marler <johnnymarler@gmail.com> Reviewded-by: Laurent Vivier <laurent@vivier.eu> Message-Id: <20200502161225.14346-1-johnnymarler@gmail.com> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
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@ -708,7 +708,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
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if (prot == 0) {
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if (prot == 0) {
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host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
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host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
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if (host_addr != MAP_FAILED && reserved_va && old_size > new_size) {
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if (host_addr != MAP_FAILED && reserved_va && old_size > new_size) {
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mmap_reserve(old_addr + old_size, new_size - old_size);
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mmap_reserve(old_addr + old_size, old_size - new_size);
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}
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}
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} else {
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} else {
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errno = ENOMEM;
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errno = ENOMEM;
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