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QElfParser: don't attempt to parse ELF files of the wrong endianness

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There's no sense in continuing to parse. We'll never be able to load
such a plugin anyway. This simplifies the code generation a lot because
now all the read<T> calls become unconditional qFromUnaligned<T>, which
is just a memcpy(), which for primitive types the compiler will simply
emit a memory load into a register.

Task-number: QTBUG-96327
Pick-to: 6.2
Change-Id: I2de1b4dfacd443148279fffd16a3574daf010635
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
This commit is contained in:
Thiago Macieira 2021-09-09 20:11:21 -07:00
parent a8083ff47a
commit 33a870afae
2 changed files with 12 additions and 21 deletions
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23
src/corelib/plugin/qelfparser_p.cpp
View File

@ -50,15 +50,15 @@ QT_BEGIN_NAMESPACE
const char *QElfParser::parseSectionHeader(const char *data, ElfSectionHeader *sh)
{
sh->name = read<qelfword_t>(data);
sh->name = qFromUnaligned<qelfword_t>(data);
data += sizeof(qelfword_t); // sh_name
sh->type = read<qelfword_t>(data);
sh->type = qFromUnaligned<qelfword_t>(data);
data += sizeof(qelfword_t) // sh_type
+ sizeof(qelfaddr_t) // sh_flags
+ sizeof(qelfaddr_t); // sh_addr
sh->offset = read<qelfoff_t>(data);
sh->offset = qFromUnaligned<qelfoff_t>(data);
data += sizeof(qelfoff_t); // sh_offset
sh->size = read<qelfoff_t>(data);
sh->size = qFromUnaligned<qelfoff_t>(data);
data += sizeof(qelfoff_t); // sh_size
return data;
}
@ -97,13 +97,14 @@ auto QElfParser::parse(const char *dataStart, ulong fdlen, const QString &librar
lib->errorString = QLibrary::tr("'%1' is an invalid ELF object (%2)").arg(library, QLibrary::tr("wrong cpu architecture"));
return Corrupt;
}
// endian
if (data[5] == 0) {
constexpr int ExpectedEndianness = (Q_BYTE_ORDER == Q_LITTLE_ENDIAN) ? 1 : 2;
if (data[5] != ExpectedEndianness) {
if (lib)
lib->errorString = QLibrary::tr("'%1' is an invalid ELF object (%2)").arg(library, QLibrary::tr("odd endianness"));
return Corrupt;
}
m_endian = (data[5] == 1 ? ElfLittleEndian : ElfBigEndian);
data += 16 // e_ident
+ sizeof(qelfhalf_t) // e_type
@ -112,11 +113,11 @@ auto QElfParser::parse(const char *dataStart, ulong fdlen, const QString &librar
+ sizeof(qelfaddr_t) // e_entry
+ sizeof(qelfoff_t); // e_phoff
qelfoff_t e_shoff = read<qelfoff_t> (data);
qelfoff_t e_shoff = qFromUnaligned<qelfoff_t> (data);
data += sizeof(qelfoff_t) // e_shoff
+ sizeof(qelfword_t); // e_flags
qelfhalf_t e_shsize = read<qelfhalf_t> (data);
qelfhalf_t e_shsize = qFromUnaligned<qelfhalf_t> (data);
if (e_shsize > fdlen) {
if (lib)
@ -128,7 +129,7 @@ auto QElfParser::parse(const char *dataStart, ulong fdlen, const QString &librar
+ sizeof(qelfhalf_t) // e_phentsize
+ sizeof(qelfhalf_t); // e_phnum
qelfhalf_t e_shentsize = read<qelfhalf_t> (data);
qelfhalf_t e_shentsize = qFromUnaligned<qelfhalf_t> (data);
if (e_shentsize % 4) {
if (lib)
@ -136,9 +137,9 @@ auto QElfParser::parse(const char *dataStart, ulong fdlen, const QString &librar
return Corrupt;
}
data += sizeof(qelfhalf_t); // e_shentsize
qelfhalf_t e_shnum = read<qelfhalf_t> (data);
qelfhalf_t e_shnum = qFromUnaligned<qelfhalf_t> (data);
data += sizeof(qelfhalf_t); // e_shnum
qelfhalf_t e_shtrndx = read<qelfhalf_t> (data);
qelfhalf_t e_shtrndx = qFromUnaligned<qelfhalf_t> (data);
data += sizeof(qelfhalf_t); // e_shtrndx
if ((quint32)(e_shnum * e_shentsize) > fdlen) {

10
src/corelib/plugin/qelfparser_p.h
View File

@ -82,19 +82,9 @@ public:
qelfoff_t size;
};
int m_endian;
int m_bits;
qelfoff_t m_stringTableFileOffset;
template <typename T>
T read(const char *s)
{
if (m_endian == ElfBigEndian)
return qFromBigEndian<T>(s);
else
return qFromLittleEndian<T>(s);
}
const char *parseSectionHeader(const char* s, ElfSectionHeader *sh);
ScanResult parse(const char *m_s, ulong fdlen, const QString &library, QLibraryPrivate *lib, qsizetype *pos, qsizetype *sectionlen);
};