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[libunwind] Avoid reading OOB for non-existent .eh_frame_hdr (#68815)

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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
8000d30814`

This change adds a ehHdr size check to avoid reading this out-of-bounds
data and potentially crashing.
This commit is contained in:
Alexander Richardson 2023-10-11 11:46:09 -07:00 committed by GitHub
parent 05181a849b
commit eb21049b4b
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1 changed files with 13 additions and 0 deletions
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13
libunwind/src/EHHeaderParser.hpp
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@ -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,