[libunwind] eb21049 - [libunwind] Avoid reading OOB for non-existent .eh_frame_hdr (#68815)
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Wed Oct 11 11:46:14 PDT 2023
Author: Alexander Richardson
Date: 2023-10-11T19:46:09+01:00
New Revision: eb21049b4b904b072679ece60e73c6b0dc0d1ebf
URL: https://github.com/llvm/llvm-project/commit/eb21049b4b904b072679ece60e73c6b0dc0d1ebf
DIFF: https://github.com/llvm/llvm-project/commit/eb21049b4b904b072679ece60e73c6b0dc0d1ebf.diff
LOG: [libunwind] Avoid reading OOB for non-existent .eh_frame_hdr (#68815)
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 ehHdr size check to avoid reading this out-of-bounds
data and potentially crashing.
Added:
Modified:
libunwind/src/EHHeaderParser.hpp
Removed:
################################################################################
diff --git a/libunwind/src/EHHeaderParser.hpp b/libunwind/src/EHHeaderParser.hpp
index ed4317c89055c9e..0662a1321e2c75e 100644
--- a/libunwind/src/EHHeaderParser.hpp
+++ b/libunwind/src/EHHeaderParser.hpp
@@ -55,6 +55,19 @@ template <typename A>
bool EHHeaderParser<A>::decodeEHHdr(A &addressSpace, pint_t ehHdrStart,
pint_t ehHdrEnd, EHHeaderInfo &ehHdrInfo) {
pint_t p = ehHdrStart;
+
+ // Ensure that we don't read data beyond the end of .eh_frame_hdr
+ if (ehHdrEnd - ehHdrStart < 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 (ehHdrEnd == ehHdrStart)
+ 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),
+ static_cast<size_t>(ehHdrEnd - ehHdrStart));
+ return false;
+ }
uint8_t version = addressSpace.get8(p++);
if (version != 1) {
_LIBUNWIND_LOG("unsupported .eh_frame_hdr version: %" PRIu8 " at %" PRIx64,
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