59 lines
2.6 KiB
Diff
59 lines
2.6 KiB
Diff
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From c09f361b41027ca073de5631c66dfe0e7275c3a4 Mon Sep 17 00:00:00 2001
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From: Kees Cook <keescook@chromium.org>
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Date: Mon, 22 Jan 2024 16:27:56 -0800
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Subject: lib: zstd: Refactor intentional wrap-around test
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In an effort to separate intentional arithmetic wrap-around from
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unexpected wrap-around, we need to refactor places that depend on this
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kind of math. One of the most common code patterns of this is:
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VAR + value < VAR
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Notably, this is considered "undefined behavior" for signed and pointer
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types, which the kernel works around by using the -fno-strict-overflow
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option in the build[1] (which used to just be -fwrapv). Regardless, we
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want to get the kernel source to the position where we can meaningfully
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instrument arithmetic wrap-around conditions and catch them when they
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are unexpected, regardless of whether they are signed[2], unsigned[3],
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or pointer[4] types.
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Switch to a more regular type for a 64-bit value and refactor the
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open-coded wrap-around addition test to use subtraction from the type max
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(since add_would_overflow() may not be defined in early boot code). This
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paves the way to enabling the wrap-around sanitizers in the future.
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Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
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Link: https://github.com/KSPP/linux/issues/26 [2]
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Link: https://github.com/KSPP/linux/issues/27 [3]
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Link: https://github.com/KSPP/linux/issues/344 [4]
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Cc: Nick Terrell <terrelln@fb.com>
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Cc: Paul Jones <paul@pauljones.id.au>
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Cc: Sedat Dilek <sedat.dilek@gmail.com>
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Cc: Oleksandr Natalenko <oleksandr@natalenko.name>
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Cc: Xin Gao <gaoxin@cdjrlc.com>
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Signed-off-by: Kees Cook <keescook@chromium.org>
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---
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lib/zstd/decompress/zstd_decompress.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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--- a/lib/zstd/decompress/zstd_decompress.c
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+++ b/lib/zstd/decompress/zstd_decompress.c
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@@ -618,7 +618,7 @@ size_t ZSTD_readSkippableFrame(void* dst
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* @return : decompressed size of the frames contained */
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unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize)
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{
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- unsigned long long totalDstSize = 0;
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+ U64 totalDstSize = 0;
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while (srcSize >= ZSTD_startingInputLength(ZSTD_f_zstd1)) {
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U32 const magicNumber = MEM_readLE32(src);
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@@ -636,7 +636,7 @@ unsigned long long ZSTD_findDecompressed
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{ unsigned long long const fcs = ZSTD_getFrameContentSize(src, srcSize);
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if (fcs >= ZSTD_CONTENTSIZE_ERROR) return fcs;
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- if (totalDstSize + fcs < totalDstSize)
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+ if (U64_MAX - totalDstSize < fcs)
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return ZSTD_CONTENTSIZE_ERROR; /* check for overflow */
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totalDstSize += fcs;
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}
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