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Relax ELF header checks - warn for apps targeting pre-O

Browse source 
Bug: http://b/32581440
Test: bionic-unit-tests --gtest_filter=dl*:Dl*
Change-Id: I2fe356c67eb9665c671758117679a29b207219e4
This commit is contained in:
Dimitry Ivanov 2016-11-16 12:29:37 -08:00
parent 60ba60dd25
commit 12b918743d
2 changed files with 30 additions and 5 deletions
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13
android-changes-for-ndk-developers.md
View file

@ -221,3 +221,16 @@ $ readelf --program-headers -W libBadFlags.so | grep WE
*Resolution*: we're aware of one middleware product that introduces these
into your app. The middleware vendor is aware of the problem and has a fix
available.
## Invalid ELF header/section headers (AOSP master)
Android loader now checks for invalid values in ELF header and section headers and fails
if they are invalid.
*Example error*
dlopen failed: "/data/data/com.example.bad/lib.so" has unsupported e_shentsize: 0x0 (expected 0x28)
*Resolution*
Do not use tools that produce invalid/malformed elf-files. Note that using them puts application
under high risk of being incompatible with future versions of Android.

22
linker/linker_phdr.cpp
View file

@ -248,14 +248,26 @@ bool ElfReader::VerifyElfHeader() {
}
if (header_.e_shentsize != sizeof(ElfW(Shdr))) {
DL_ERR("\"%s\" has unsupported e_shentsize: 0x%x (expected 0x%zx)",
name_.c_str(), header_.e_shentsize, sizeof(ElfW(Shdr)));
return false;
// Fail if app is targeting Android O or above
if (get_application_target_sdk_version() >= __ANDROID_API_O__) {
DL_ERR_AND_LOG("\"%s\" has unsupported e_shentsize: 0x%x (expected 0x%zx)",
name_.c_str(), header_.e_shentsize, sizeof(ElfW(Shdr)));
return false;
}
DL_WARN("\"%s\" has unsupported e_shentsize: 0x%x (expected 0x%zx)",
name_.c_str(), header_.e_shentsize, sizeof(ElfW(Shdr)));
add_dlwarning(name_.c_str(), "has invalid ELF header");
}
if (header_.e_shstrndx == 0) {
DL_ERR("\"%s\" has invalid e_shstrndx", name_.c_str());
return false;
// Fail if app is targeting Android O or above
if (get_application_target_sdk_version() >= __ANDROID_API_O__) {
DL_ERR_AND_LOG("\"%s\" has invalid e_shstrndx", name_.c_str());
return false;
}
DL_WARN("\"%s\" has invalid e_shstrndx", name_.c_str());
add_dlwarning(name_.c_str(), "has invalid ELF header");
}
return true;