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Fixes for static PIE executables #166

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Fixes for static PIE executables #166

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c3ffe62
rewriteSectionsLibrary: assume all libraries may be executable; fixes…
rcombs Jun 16, 2020
5daa357
modifyRPath: when possible, avoid growing the dynamic section
Mar 30, 2019
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11 changes: 3 additions & 8 deletions src/patchelf.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -106,8 +106,6 @@ class ElfFile

bool changed = false;

bool isExecutable = false;

typedef std::string SectionName;
typedef std::map<SectionName, std::string> ReplacedSections;

Expand Down Expand Up @@ -415,10 +413,8 @@ ElfFile<ElfFileParamNames>::ElfFile(FileContents fileContents)
error("program headers have wrong size");

/* Copy the program and section headers. */
for (int i = 0; i < rdi(hdr->e_phnum); ++i) {
for (int i = 0; i < rdi(hdr->e_phnum); ++i)
phdrs.push_back(* ((Elf_Phdr *) (contents + rdi(hdr->e_phoff)) + i));
if (rdi(phdrs[i].p_type) == PT_INTERP) isExecutable = true;
}

for (int i = 0; i < rdi(hdr->e_shnum); ++i)
shdrs.push_back(* ((Elf_Shdr *) (contents + rdi(hdr->e_shoff)) + i));
Expand Down Expand Up @@ -741,10 +737,9 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
since DYN executables tend to start at virtual address 0, so
rewriteSectionsExecutable() won't work because it doesn't have
any virtual address space to grow downwards into. */
if (isExecutable && startOffset > startPage) {
if (startOffset > startPage)
debug("shifting new PT_LOAD segment by %d bytes to work around a Linux kernel bug\n", startOffset - startPage);
startPage = startOffset;
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@Mic92 Mic92 Jul 31, 2020

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This disables this mitigation?

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@Mic92 Mic92 Jul 31, 2020

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no, it unconditionally applies it...

}
startPage = startOffset;
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@Mic92 Mic92 Aug 21, 2021

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I understand why isExecutable was removed as a conditional but not why startPage = startOffset was moved out.


/* Add a segment that maps the replaced sections into memory. */
wri(hdr->e_phoff, sizeof(Elf_Ehdr));
Expand Down