s390/modules: add relocation overflow checking
Given enough debug options some modules can grow large enough that the GOT table gets bigger than 4K. On s390 the modules are compiled with -fpic which limits the GOT to 4K. The end result is a module that is loaded but won't work. Add a sanity check to apply_rela and return with an error if a relocation error is detected for a module. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
parent
4d334fd155
commit
083e14c09b
@ -65,8 +65,7 @@ void module_free(struct module *mod, void *module_region)
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vfree(module_region);
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}
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static void
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check_rela(Elf_Rela *rela, struct module *me)
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static void check_rela(Elf_Rela *rela, struct module *me)
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{
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struct mod_arch_syminfo *info;
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@ -115,9 +114,8 @@ check_rela(Elf_Rela *rela, struct module *me)
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* Account for GOT and PLT relocations. We can't add sections for
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* got and plt but we can increase the core module size.
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*/
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int
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module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
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char *secstrings, struct module *me)
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int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
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char *secstrings, struct module *me)
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{
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Elf_Shdr *symtab;
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Elf_Sym *symbols;
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@ -179,13 +177,52 @@ module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
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return 0;
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}
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static int
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apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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struct module *me)
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static int apply_rela_bits(Elf_Addr loc, Elf_Addr val,
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int sign, int bits, int shift)
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{
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unsigned long umax;
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long min, max;
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if (val & ((1UL << shift) - 1))
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return -ENOEXEC;
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if (sign) {
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val = (Elf_Addr)(((long) val) >> shift);
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min = -(1L << (bits - 1));
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max = (1L << (bits - 1)) - 1;
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if ((long) val < min || (long) val > max)
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return -ENOEXEC;
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} else {
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val >>= shift;
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umax = ((1UL << (bits - 1)) << 1) - 1;
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if ((unsigned long) val > umax)
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return -ENOEXEC;
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}
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if (bits == 8)
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*(unsigned char *) loc = val;
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else if (bits == 12)
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*(unsigned short *) loc = (val & 0xfff) |
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(*(unsigned short *) loc & 0xf000);
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else if (bits == 16)
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*(unsigned short *) loc = val;
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else if (bits == 20)
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*(unsigned int *) loc = (val & 0xfff) << 16 |
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(val & 0xff000) >> 4 |
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(*(unsigned int *) loc & 0xf00000ff);
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else if (bits == 32)
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*(unsigned int *) loc = val;
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else if (bits == 64)
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*(unsigned long *) loc = val;
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return 0;
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}
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static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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const char *strtab, struct module *me)
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{
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struct mod_arch_syminfo *info;
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Elf_Addr loc, val;
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int r_type, r_sym;
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int rc;
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/* This is where to make the change */
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loc = base + rela->r_offset;
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@ -205,20 +242,17 @@ apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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case R_390_64: /* Direct 64 bit. */
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val += rela->r_addend;
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if (r_type == R_390_8)
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*(unsigned char *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 8, 0);
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else if (r_type == R_390_12)
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*(unsigned short *) loc = (val & 0xfff) |
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(*(unsigned short *) loc & 0xf000);
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rc = apply_rela_bits(loc, val, 0, 12, 0);
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else if (r_type == R_390_16)
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*(unsigned short *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 16, 0);
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else if (r_type == R_390_20)
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*(unsigned int *) loc =
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(*(unsigned int *) loc & 0xf00000ff) |
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(val & 0xfff) << 16 | (val & 0xff000) >> 4;
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rc = apply_rela_bits(loc, val, 1, 20, 0);
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else if (r_type == R_390_32)
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*(unsigned int *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 32, 0);
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else if (r_type == R_390_64)
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*(unsigned long *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 64, 0);
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break;
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case R_390_PC16: /* PC relative 16 bit. */
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case R_390_PC16DBL: /* PC relative 16 bit shifted by 1. */
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@ -227,15 +261,15 @@ apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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case R_390_PC64: /* PC relative 64 bit. */
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val += rela->r_addend - loc;
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if (r_type == R_390_PC16)
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*(unsigned short *) loc = val;
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rc = apply_rela_bits(loc, val, 1, 16, 0);
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else if (r_type == R_390_PC16DBL)
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*(unsigned short *) loc = val >> 1;
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rc = apply_rela_bits(loc, val, 1, 16, 1);
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else if (r_type == R_390_PC32DBL)
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*(unsigned int *) loc = val >> 1;
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rc = apply_rela_bits(loc, val, 1, 32, 1);
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else if (r_type == R_390_PC32)
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*(unsigned int *) loc = val;
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rc = apply_rela_bits(loc, val, 1, 32, 0);
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else if (r_type == R_390_PC64)
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*(unsigned long *) loc = val;
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rc = apply_rela_bits(loc, val, 1, 64, 0);
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break;
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case R_390_GOT12: /* 12 bit GOT offset. */
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case R_390_GOT16: /* 16 bit GOT offset. */
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@ -260,26 +294,24 @@ apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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val = info->got_offset + rela->r_addend;
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if (r_type == R_390_GOT12 ||
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r_type == R_390_GOTPLT12)
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*(unsigned short *) loc = (val & 0xfff) |
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(*(unsigned short *) loc & 0xf000);
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rc = apply_rela_bits(loc, val, 0, 12, 0);
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else if (r_type == R_390_GOT16 ||
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r_type == R_390_GOTPLT16)
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*(unsigned short *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 16, 0);
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else if (r_type == R_390_GOT20 ||
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r_type == R_390_GOTPLT20)
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*(unsigned int *) loc =
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(*(unsigned int *) loc & 0xf00000ff) |
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(val & 0xfff) << 16 | (val & 0xff000) >> 4;
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rc = apply_rela_bits(loc, val, 1, 20, 0);
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else if (r_type == R_390_GOT32 ||
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r_type == R_390_GOTPLT32)
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*(unsigned int *) loc = val;
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else if (r_type == R_390_GOTENT ||
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r_type == R_390_GOTPLTENT)
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*(unsigned int *) loc =
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(val + (Elf_Addr) me->module_core - loc) >> 1;
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rc = apply_rela_bits(loc, val, 0, 32, 0);
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else if (r_type == R_390_GOT64 ||
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r_type == R_390_GOTPLT64)
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*(unsigned long *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 64, 0);
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else if (r_type == R_390_GOTENT ||
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r_type == R_390_GOTPLTENT) {
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val += (Elf_Addr) me->module_core - loc;
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rc = apply_rela_bits(loc, val, 1, 32, 1);
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}
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break;
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case R_390_PLT16DBL: /* 16 bit PC rel. PLT shifted by 1. */
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case R_390_PLT32DBL: /* 32 bit PC rel. PLT shifted by 1. */
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@ -321,17 +353,17 @@ apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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val += rela->r_addend - loc;
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}
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if (r_type == R_390_PLT16DBL)
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*(unsigned short *) loc = val >> 1;
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rc = apply_rela_bits(loc, val, 1, 16, 1);
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else if (r_type == R_390_PLTOFF16)
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*(unsigned short *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 16, 0);
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else if (r_type == R_390_PLT32DBL)
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*(unsigned int *) loc = val >> 1;
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rc = apply_rela_bits(loc, val, 1, 32, 1);
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else if (r_type == R_390_PLT32 ||
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r_type == R_390_PLTOFF32)
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*(unsigned int *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 32, 0);
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else if (r_type == R_390_PLT64 ||
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r_type == R_390_PLTOFF64)
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*(unsigned long *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 64, 0);
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break;
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case R_390_GOTOFF16: /* 16 bit offset to GOT. */
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case R_390_GOTOFF32: /* 32 bit offset to GOT. */
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@ -339,20 +371,20 @@ apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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val = val + rela->r_addend -
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((Elf_Addr) me->module_core + me->arch.got_offset);
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if (r_type == R_390_GOTOFF16)
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*(unsigned short *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 16, 0);
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else if (r_type == R_390_GOTOFF32)
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*(unsigned int *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 32, 0);
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else if (r_type == R_390_GOTOFF64)
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*(unsigned long *) loc = val;
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rc = apply_rela_bits(loc, val, 0, 64, 0);
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break;
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case R_390_GOTPC: /* 32 bit PC relative offset to GOT. */
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case R_390_GOTPCDBL: /* 32 bit PC rel. off. to GOT shifted by 1. */
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val = (Elf_Addr) me->module_core + me->arch.got_offset +
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rela->r_addend - loc;
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if (r_type == R_390_GOTPC)
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*(unsigned int *) loc = val;
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rc = apply_rela_bits(loc, val, 1, 32, 0);
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else if (r_type == R_390_GOTPCDBL)
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*(unsigned int *) loc = val >> 1;
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rc = apply_rela_bits(loc, val, 1, 32, 1);
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break;
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case R_390_COPY:
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case R_390_GLOB_DAT: /* Create GOT entry. */
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@ -360,19 +392,25 @@ apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
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case R_390_RELATIVE: /* Adjust by program base. */
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/* Only needed if we want to support loading of
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modules linked with -shared. */
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break;
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return -ENOEXEC;
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default:
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printk(KERN_ERR "module %s: Unknown relocation: %u\n",
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printk(KERN_ERR "module %s: unknown relocation: %u\n",
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me->name, r_type);
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return -ENOEXEC;
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}
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if (rc) {
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printk(KERN_ERR "module %s: relocation error for symbol %s "
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"(r_type %i, value 0x%lx)\n",
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me->name, strtab + symtab[r_sym].st_name,
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r_type, (unsigned long) val);
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return rc;
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}
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return 0;
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}
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int
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apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
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unsigned int symindex, unsigned int relsec,
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struct module *me)
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int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
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unsigned int symindex, unsigned int relsec,
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struct module *me)
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{
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Elf_Addr base;
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Elf_Sym *symtab;
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@ -388,7 +426,7 @@ apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
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n = sechdrs[relsec].sh_size / sizeof(Elf_Rela);
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for (i = 0; i < n; i++, rela++) {
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rc = apply_rela(rela, base, symtab, me);
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rc = apply_rela(rela, base, symtab, strtab, me);
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if (rc)
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return rc;
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}
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