llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-libunwind Author: Alexander Richardson (arichardson) <details> <summary>Changes</summary> I was running the tests with baremetal picolibc which has a linker script that __eh_frame_start==__eh_frame_end (not equal to zero) in case there is no .eh_frame_hdr. I noticed that libunwind was trying to read nonsense data because it was printing messages such as `libunwind: unsupported .eh_frame_hdr version: 20 at https://github.com/llvm/llvm-project/commit/8000d308146ebf49cb364cb600e28a0a42e22c83` This change adds a ehHdrSize check to avoid reading this out-of-bounds data and potentially crashing. Depends on #<!-- -->68813 which I've included as the first commit here (not sure how to sensibly do stacked PRs). --- Full diff: https://github.com/llvm/llvm-project/pull/68815.diff 1 Files Affected: - (modified) libunwind/src/EHHeaderParser.hpp (+16-3) ``````````diff diff --git a/libunwind/src/EHHeaderParser.hpp b/libunwind/src/EHHeaderParser.hpp index ed4317c89055c9e..8d37594e7b9be89 100644 --- a/libunwind/src/EHHeaderParser.hpp +++ b/libunwind/src/EHHeaderParser.hpp @@ -35,7 +35,7 @@ template <typename A> class EHHeaderParser { uint8_t table_enc; }; - static bool decodeEHHdr(A &addressSpace, pint_t ehHdrStart, pint_t ehHdrEnd, + static bool decodeEHHdr(A &addressSpace, pint_t ehHdrStart, size_t ehHdrSize, EHHeaderInfo &ehHdrInfo); static bool findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart, uint32_t sectionLength, @@ -53,8 +53,21 @@ template <typename A> class EHHeaderParser { template <typename A> bool EHHeaderParser<A>::decodeEHHdr(A &addressSpace, pint_t ehHdrStart, - pint_t ehHdrEnd, EHHeaderInfo &ehHdrInfo) { + size_t ehHdrSize, EHHeaderInfo &ehHdrInfo) { pint_t p = ehHdrStart; + pint_t ehHdrEnd = ehHdrStart + ehHdrSize; + + // Ensure that we don't read data beyond the end of .eh_frame_hdr + if (ehHdrSize < 4) { + // Don't print a message for an empty .eh_frame_hdr (this can happen if + // the linker script defines symbols for it even in the empty case). + if (ehHdrSize == 0) + return false; + _LIBUNWIND_LOG("unsupported .eh_frame_hdr at %" PRIx64 + ": need at least 4 bytes of data but only got %zd", + static_cast<uint64_t>(ehHdrStart), ehHdrSize); + return false; + } uint8_t version = addressSpace.get8(p++); if (version != 1) { _LIBUNWIND_LOG("unsupported .eh_frame_hdr version: %" PRIu8 " at %" PRIx64, @@ -106,7 +119,7 @@ bool EHHeaderParser<A>::findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart, pint_t ehHdrEnd = ehHdrStart + sectionLength; EHHeaderParser<A>::EHHeaderInfo hdrInfo; - if (!EHHeaderParser<A>::decodeEHHdr(addressSpace, ehHdrStart, ehHdrEnd, + if (!EHHeaderParser<A>::decodeEHHdr(addressSpace, ehHdrStart, sectionLength, hdrInfo)) return false; `````````` </details> https://github.com/llvm/llvm-project/pull/68815 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits