rtld: fix SysV hash function overflow
Quoting from https://maskray.me/blog/2023-04-12-elf-hash-function: The System V Application Binary Interface (generic ABI) specifies the ELF object file format. When producing an output executable or shared object needing a dynamic symbol table (.dynsym), a linker generates a .hash section with type SHT_HASH to hold a symbol hash table. A DT_HASH tag is produced to hold the address of .hash. The function is supposed to return a value no larger than 0x0fffffff. Unfortunately, there is a bug. When unsigned long consists of more than 32 bits, the return value may be larger than UINT32_MAX. For instance, elf_hash((const unsigned char *)"\xff\x0f\x0f\x0f\x0f\x0f\x12") returns 0x100000002, which is clearly unintended, as the function should behave the same way regardless of whether long represents a 32-bit integer or a 64-bit integer. Reviewed by: kib, Fangrui Song Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D39517
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@ -1796,23 +1796,20 @@ donelist_check(DoneList *dlp, const Obj_Entry *obj)
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}
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/*
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* Hash function for symbol table lookup. Don't even think about changing
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* this. It is specified by the System V ABI.
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* SysV hash function for symbol table lookup. It is a slightly optimized
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* version of the hash specified by the System V ABI.
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*/
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unsigned long
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Elf32_Word
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elf_hash(const char *name)
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{
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const unsigned char *p = (const unsigned char *)name;
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unsigned long h = 0;
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unsigned long g;
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Elf32_Word h = 0;
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while (*p != '\0') {
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h = (h << 4) + *p++;
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if ((g = h & 0xf0000000) != 0)
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h ^= g >> 24;
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h &= ~g;
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h ^= (h >> 24) & 0xf0;
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}
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return (h);
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return (h & 0x0fffffff);
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}
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/*
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@ -379,7 +379,7 @@ void dump_Elf_Rela(Obj_Entry *, const Elf_Rela *, u_long);
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*/
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uintptr_t rtld_round_page(uintptr_t);
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uintptr_t rtld_trunc_page(uintptr_t);
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unsigned long elf_hash(const char *);
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Elf32_Word elf_hash(const char *);
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const Elf_Sym *find_symdef(unsigned long, const Obj_Entry *,
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const Obj_Entry **, int, SymCache *, struct Struct_RtldLockState *);
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void lockdflt_init(void);
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