[linux-stable-rc:queue/5.10 9690/9999] fs/binfmt_elf.c:823:16: warning: variable 'load_addr' set but not used

From: kernel test robot
Date: Tue Apr 12 2022 - 04:57:45 EST

tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git queue/5.10
head: 3a166b51d36ae1f85bed764b7c07a6ca6d6c73a1
commit: dd85ed4af8f5cb42990fb5f42c22d268028693a3 [9690/9999] fs/binfmt_elf: Fix AT_PHDR for unusual ELF files
config: powerpc-pseries_defconfig (https://download.01.org/0day-ci/archive/20220412/202204121527.yG4uNLH6-lkp@xxxxxxxxx/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project c6e83f560f06cdfe8aa47b248d8bdc58f947274b)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install powerpc cross compiling tool for clang build
# apt-get install binutils-powerpc-linux-gnu
# https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/commit/?id=dd85ed4af8f5cb42990fb5f42c22d268028693a3
git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
git fetch --no-tags linux-stable-rc queue/5.10
git checkout dd85ed4af8f5cb42990fb5f42c22d268028693a3
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> fs/binfmt_elf.c:823:16: warning: variable 'load_addr' set but not used [-Wunused-but-set-variable]
unsigned long load_addr, load_bias = 0, phdr_addr = 0;
^
1 warning generated.


vim +/load_addr +823 fs/binfmt_elf.c

819
820 static int load_elf_binary(struct linux_binprm *bprm)
821 {
822 struct file *interpreter = NULL; /* to shut gcc up */
> 823 unsigned long load_addr, load_bias = 0, phdr_addr = 0;
824 int load_addr_set = 0;
825 unsigned long error;
826 struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
827 struct elf_phdr *elf_property_phdata = NULL;
828 unsigned long elf_bss, elf_brk;
829 int bss_prot = 0;
830 int retval, i;
831 unsigned long elf_entry;
832 unsigned long e_entry;
833 unsigned long interp_load_addr = 0;
834 unsigned long start_code, end_code, start_data, end_data;
835 unsigned long reloc_func_desc __maybe_unused = 0;
836 int executable_stack = EXSTACK_DEFAULT;
837 struct elfhdr *elf_ex = (struct elfhdr *)bprm->buf;
838 struct elfhdr *interp_elf_ex = NULL;
839 struct arch_elf_state arch_state = INIT_ARCH_ELF_STATE;
840 struct mm_struct *mm;
841 struct pt_regs *regs;
842
843 retval = -ENOEXEC;
844 /* First of all, some simple consistency checks */
845 if (memcmp(elf_ex->e_ident, ELFMAG, SELFMAG) != 0)
846 goto out;
847
848 if (elf_ex->e_type != ET_EXEC && elf_ex->e_type != ET_DYN)
849 goto out;
850 if (!elf_check_arch(elf_ex))
851 goto out;
852 if (elf_check_fdpic(elf_ex))
853 goto out;
854 if (!bprm->file->f_op->mmap)
855 goto out;
856
857 elf_phdata = load_elf_phdrs(elf_ex, bprm->file);
858 if (!elf_phdata)
859 goto out;
860
861 elf_ppnt = elf_phdata;
862 for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++) {
863 char *elf_interpreter;
864
865 if (elf_ppnt->p_type == PT_GNU_PROPERTY) {
866 elf_property_phdata = elf_ppnt;
867 continue;
868 }
869
870 if (elf_ppnt->p_type != PT_INTERP)
871 continue;
872
873 /*
874 * This is the program interpreter used for shared libraries -
875 * for now assume that this is an a.out format binary.
876 */
877 retval = -ENOEXEC;
878 if (elf_ppnt->p_filesz > PATH_MAX || elf_ppnt->p_filesz < 2)
879 goto out_free_ph;
880
881 retval = -ENOMEM;
882 elf_interpreter = kmalloc(elf_ppnt->p_filesz, GFP_KERNEL);
883 if (!elf_interpreter)
884 goto out_free_ph;
885
886 retval = elf_read(bprm->file, elf_interpreter, elf_ppnt->p_filesz,
887 elf_ppnt->p_offset);
888 if (retval < 0)
889 goto out_free_interp;
890 /* make sure path is NULL terminated */
891 retval = -ENOEXEC;
892 if (elf_interpreter[elf_ppnt->p_filesz - 1] != '\0')
893 goto out_free_interp;
894
895 interpreter = open_exec(elf_interpreter);
896 kfree(elf_interpreter);
897 retval = PTR_ERR(interpreter);
898 if (IS_ERR(interpreter))
899 goto out_free_ph;
900
901 /*
902 * If the binary is not readable then enforce mm->dumpable = 0
903 * regardless of the interpreter's permissions.
904 */
905 would_dump(bprm, interpreter);
906
907 interp_elf_ex = kmalloc(sizeof(*interp_elf_ex), GFP_KERNEL);
908 if (!interp_elf_ex) {
909 retval = -ENOMEM;
910 goto out_free_ph;
911 }
912
913 /* Get the exec headers */
914 retval = elf_read(interpreter, interp_elf_ex,
915 sizeof(*interp_elf_ex), 0);
916 if (retval < 0)
917 goto out_free_dentry;
918
919 break;
920
921 out_free_interp:
922 kfree(elf_interpreter);
923 goto out_free_ph;
924 }
925
926 elf_ppnt = elf_phdata;
927 for (i = 0; i < elf_ex->e_phnum; i++, elf_ppnt++)
928 switch (elf_ppnt->p_type) {
929 case PT_GNU_STACK:
930 if (elf_ppnt->p_flags & PF_X)
931 executable_stack = EXSTACK_ENABLE_X;
932 else
933 executable_stack = EXSTACK_DISABLE_X;
934 break;
935
936 case PT_LOPROC ... PT_HIPROC:
937 retval = arch_elf_pt_proc(elf_ex, elf_ppnt,
938 bprm->file, false,
939 &arch_state);
940 if (retval)
941 goto out_free_dentry;
942 break;
943 }
944
945 /* Some simple consistency checks for the interpreter */
946 if (interpreter) {
947 retval = -ELIBBAD;
948 /* Not an ELF interpreter */
949 if (memcmp(interp_elf_ex->e_ident, ELFMAG, SELFMAG) != 0)
950 goto out_free_dentry;
951 /* Verify the interpreter has a valid arch */
952 if (!elf_check_arch(interp_elf_ex) ||
953 elf_check_fdpic(interp_elf_ex))
954 goto out_free_dentry;
955
956 /* Load the interpreter program headers */
957 interp_elf_phdata = load_elf_phdrs(interp_elf_ex,
958 interpreter);
959 if (!interp_elf_phdata)
960 goto out_free_dentry;
961
962 /* Pass PT_LOPROC..PT_HIPROC headers to arch code */
963 elf_property_phdata = NULL;
964 elf_ppnt = interp_elf_phdata;
965 for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++)
966 switch (elf_ppnt->p_type) {
967 case PT_GNU_PROPERTY:
968 elf_property_phdata = elf_ppnt;
969 break;
970
971 case PT_LOPROC ... PT_HIPROC:
972 retval = arch_elf_pt_proc(interp_elf_ex,
973 elf_ppnt, interpreter,
974 true, &arch_state);
975 if (retval)
976 goto out_free_dentry;
977 break;
978 }
979 }
980
981 retval = parse_elf_properties(interpreter ?: bprm->file,
982 elf_property_phdata, &arch_state);
983 if (retval)
984 goto out_free_dentry;
985
986 /*
987 * Allow arch code to reject the ELF at this point, whilst it's
988 * still possible to return an error to the code that invoked
989 * the exec syscall.
990 */
991 retval = arch_check_elf(elf_ex,
992 !!interpreter, interp_elf_ex,
993 &arch_state);
994 if (retval)
995 goto out_free_dentry;
996
997 /* Flush all traces of the currently running executable */
998 retval = begin_new_exec(bprm);
999 if (retval)
1000 goto out_free_dentry;
1001
1002 /* Do this immediately, since STACK_TOP as used in setup_arg_pages
1003 may depend on the personality. */
1004 SET_PERSONALITY2(*elf_ex, &arch_state);
1005 if (elf_read_implies_exec(*elf_ex, executable_stack))
1006 current->personality |= READ_IMPLIES_EXEC;
1007
1008 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
1009 current->flags |= PF_RANDOMIZE;
1010
1011 setup_new_exec(bprm);
1012
1013 /* Do this so that we can load the interpreter, if need be. We will
1014 change some of these later */
1015 retval = setup_arg_pages(bprm, randomize_stack_top(STACK_TOP),
1016 executable_stack);
1017 if (retval < 0)
1018 goto out_free_dentry;
1019
1020 elf_bss = 0;
1021 elf_brk = 0;
1022
1023 start_code = ~0UL;
1024 end_code = 0;
1025 start_data = 0;
1026 end_data = 0;
1027
1028 /* Now we do a little grungy work by mmapping the ELF image into
1029 the correct location in memory. */
1030 for(i = 0, elf_ppnt = elf_phdata;
1031 i < elf_ex->e_phnum; i++, elf_ppnt++) {
1032 int elf_prot, elf_flags;
1033 unsigned long k, vaddr;
1034 unsigned long total_size = 0;
1035 unsigned long alignment;
1036
1037 if (elf_ppnt->p_type != PT_LOAD)
1038 continue;
1039
1040 if (unlikely (elf_brk > elf_bss)) {
1041 unsigned long nbyte;
1042
1043 /* There was a PT_LOAD segment with p_memsz > p_filesz
1044 before this one. Map anonymous pages, if needed,
1045 and clear the area. */
1046 retval = set_brk(elf_bss + load_bias,
1047 elf_brk + load_bias,
1048 bss_prot);
1049 if (retval)
1050 goto out_free_dentry;
1051 nbyte = ELF_PAGEOFFSET(elf_bss);
1052 if (nbyte) {
1053 nbyte = ELF_MIN_ALIGN - nbyte;
1054 if (nbyte > elf_brk - elf_bss)
1055 nbyte = elf_brk - elf_bss;
1056 if (clear_user((void __user *)elf_bss +
1057 load_bias, nbyte)) {
1058 /*
1059 * This bss-zeroing can fail if the ELF
1060 * file specifies odd protections. So
1061 * we don't check the return value
1062 */
1063 }
1064 }
1065 }
1066
1067 elf_prot = make_prot(elf_ppnt->p_flags, &arch_state,
1068 !!interpreter, false);
1069
1070 elf_flags = MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE;
1071
1072 vaddr = elf_ppnt->p_vaddr;
1073 /*
1074 * If we are loading ET_EXEC or we have already performed
1075 * the ET_DYN load_addr calculations, proceed normally.
1076 */
1077 if (elf_ex->e_type == ET_EXEC || load_addr_set) {
1078 elf_flags |= MAP_FIXED;
1079 } else if (elf_ex->e_type == ET_DYN) {
1080 /*
1081 * This logic is run once for the first LOAD Program
1082 * Header for ET_DYN binaries to calculate the
1083 * randomization (load_bias) for all the LOAD
1084 * Program Headers, and to calculate the entire
1085 * size of the ELF mapping (total_size). (Note that
1086 * load_addr_set is set to true later once the
1087 * initial mapping is performed.)
1088 *
1089 * There are effectively two types of ET_DYN
1090 * binaries: programs (i.e. PIE: ET_DYN with INTERP)
1091 * and loaders (ET_DYN without INTERP, since they
1092 * _are_ the ELF interpreter). The loaders must
1093 * be loaded away from programs since the program
1094 * may otherwise collide with the loader (especially
1095 * for ET_EXEC which does not have a randomized
1096 * position). For example to handle invocations of
1097 * "./ld.so someprog" to test out a new version of
1098 * the loader, the subsequent program that the
1099 * loader loads must avoid the loader itself, so
1100 * they cannot share the same load range. Sufficient
1101 * room for the brk must be allocated with the
1102 * loader as well, since brk must be available with
1103 * the loader.
1104 *
1105 * Therefore, programs are loaded offset from
1106 * ELF_ET_DYN_BASE and loaders are loaded into the
1107 * independently randomized mmap region (0 load_bias
1108 * without MAP_FIXED).
1109 */
1110 if (interpreter) {
1111 load_bias = ELF_ET_DYN_BASE;
1112 if (current->flags & PF_RANDOMIZE)
1113 load_bias += arch_mmap_rnd();
1114 alignment = maximum_alignment(elf_phdata, elf_ex->e_phnum);
1115 if (alignment)
1116 load_bias &= ~(alignment - 1);
1117 elf_flags |= MAP_FIXED;
1118 } else
1119 load_bias = 0;
1120
1121 /*
1122 * Since load_bias is used for all subsequent loading
1123 * calculations, we must lower it by the first vaddr
1124 * so that the remaining calculations based on the
1125 * ELF vaddrs will be correctly offset. The result
1126 * is then page aligned.
1127 */
1128 load_bias = ELF_PAGESTART(load_bias - vaddr);
1129
1130 total_size = total_mapping_size(elf_phdata,
1131 elf_ex->e_phnum);
1132 if (!total_size) {
1133 retval = -EINVAL;
1134 goto out_free_dentry;
1135 }
1136 }
1137
1138 error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt,
1139 elf_prot, elf_flags, total_size);
1140 if (BAD_ADDR(error)) {
1141 retval = IS_ERR((void *)error) ?
1142 PTR_ERR((void*)error) : -EINVAL;
1143 goto out_free_dentry;
1144 }
1145
1146 if (!load_addr_set) {
1147 load_addr_set = 1;
1148 load_addr = (elf_ppnt->p_vaddr - elf_ppnt->p_offset);
1149 if (elf_ex->e_type == ET_DYN) {
1150 load_bias += error -
1151 ELF_PAGESTART(load_bias + vaddr);
1152 load_addr += load_bias;
1153 reloc_func_desc = load_bias;
1154 }
1155 }
1156
1157 /*
1158 * Figure out which segment in the file contains the Program
1159 * Header table, and map to the associated memory address.
1160 */
1161 if (elf_ppnt->p_offset <= elf_ex->e_phoff &&
1162 elf_ex->e_phoff < elf_ppnt->p_offset + elf_ppnt->p_filesz) {
1163 phdr_addr = elf_ex->e_phoff - elf_ppnt->p_offset +
1164 elf_ppnt->p_vaddr;
1165 }
1166
1167 k = elf_ppnt->p_vaddr;
1168 if ((elf_ppnt->p_flags & PF_X) && k < start_code)
1169 start_code = k;
1170 if (start_data < k)
1171 start_data = k;
1172
1173 /*
1174 * Check to see if the section's size will overflow the
1175 * allowed task size. Note that p_filesz must always be
1176 * <= p_memsz so it is only necessary to check p_memsz.
1177 */
1178 if (BAD_ADDR(k) || elf_ppnt->p_filesz > elf_ppnt->p_memsz ||
1179 elf_ppnt->p_memsz > TASK_SIZE ||
1180 TASK_SIZE - elf_ppnt->p_memsz < k) {
1181 /* set_brk can never work. Avoid overflows. */
1182 retval = -EINVAL;
1183 goto out_free_dentry;
1184 }
1185
1186 k = elf_ppnt->p_vaddr + elf_ppnt->p_filesz;
1187
1188 if (k > elf_bss)
1189 elf_bss = k;
1190 if ((elf_ppnt->p_flags & PF_X) && end_code < k)
1191 end_code = k;
1192 if (end_data < k)
1193 end_data = k;
1194 k = elf_ppnt->p_vaddr + elf_ppnt->p_memsz;
1195 if (k > elf_brk) {
1196 bss_prot = elf_prot;
1197 elf_brk = k;
1198 }
1199 }
1200
1201 e_entry = elf_ex->e_entry + load_bias;
1202 phdr_addr += load_bias;
1203 elf_bss += load_bias;
1204 elf_brk += load_bias;
1205 start_code += load_bias;
1206 end_code += load_bias;
1207 start_data += load_bias;
1208 end_data += load_bias;
1209
1210 /* Calling set_brk effectively mmaps the pages that we need
1211 * for the bss and break sections. We must do this before
1212 * mapping in the interpreter, to make sure it doesn't wind
1213 * up getting placed where the bss needs to go.
1214 */
1215 retval = set_brk(elf_bss, elf_brk, bss_prot);
1216 if (retval)
1217 goto out_free_dentry;
1218 if (likely(elf_bss != elf_brk) && unlikely(padzero(elf_bss))) {
1219 retval = -EFAULT; /* Nobody gets to see this, but.. */
1220 goto out_free_dentry;
1221 }
1222
1223 if (interpreter) {
1224 elf_entry = load_elf_interp(interp_elf_ex,
1225 interpreter,
1226 load_bias, interp_elf_phdata,
1227 &arch_state);
1228 if (!IS_ERR((void *)elf_entry)) {
1229 /*
1230 * load_elf_interp() returns relocation
1231 * adjustment
1232 */
1233 interp_load_addr = elf_entry;
1234 elf_entry += interp_elf_ex->e_entry;
1235 }
1236 if (BAD_ADDR(elf_entry)) {
1237 retval = IS_ERR((void *)elf_entry) ?
1238 (int)elf_entry : -EINVAL;
1239 goto out_free_dentry;
1240 }
1241 reloc_func_desc = interp_load_addr;
1242
1243 allow_write_access(interpreter);
1244 fput(interpreter);
1245
1246 kfree(interp_elf_ex);
1247 kfree(interp_elf_phdata);
1248 } else {
1249 elf_entry = e_entry;
1250 if (BAD_ADDR(elf_entry)) {
1251 retval = -EINVAL;
1252 goto out_free_dentry;
1253 }
1254 }
1255
1256 kfree(elf_phdata);
1257
1258 set_binfmt(&elf_format);
1259

--
0-DAY CI Kernel Test Service
https://01.org/lkp