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Fix broken mmap() usage in nlist() by switching to pread()

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The offset is not page aligned, which makes mmap() return EINVAL on
Linux. Switch to use pread() which handles unaligned offset and non-page
sized reads, and because we are already loading parts of the executable
by read() calls, so there's not much point in using mmap() anyway.
This commit is contained in:
Guillem Jover 2017-06-14 01:49:25 +02:00
parent e8d340de9e
commit 47013bc92a
1 changed files with 16 additions and 15 deletions
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31
src/nlist.c
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@ -36,6 +36,7 @@
#include <errno.h> #include <errno.h>
#include <fcntl.h> #include <fcntl.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h>
#include <string.h> #include <string.h>
#include <unistd.h> #include <unistd.h>
#include <nlist.h> #include <nlist.h>
@ -131,7 +132,6 @@ __fdnlist(int fd, struct nlist *list)
char *strtab = NULL; char *strtab = NULL;
Elf_Shdr *shdr = NULL; Elf_Shdr *shdr = NULL;
Elf_Word shdr_size; Elf_Word shdr_size;
void *base;
struct stat st; struct stat st;
/* Make sure obj is OK */ /* Make sure obj is OK */
@ -150,12 +150,13 @@ __fdnlist(int fd, struct nlist *list)
return (-1); return (-1);
} }
/* mmap section header table */ shdr = malloc((size_t)shdr_size);
base = mmap(NULL, (size_t)shdr_size, PROT_READ, 0, fd, if (shdr == NULL)
(off_t)ehdr.e_shoff);
if (base == MAP_FAILED)
return (-1); return (-1);
shdr = (Elf_Shdr *)base;
/* Load section header table. */
if (pread(fd, shdr, (size_t)shdr_size, (off_t)ehdr.e_shoff) < 0)
goto done;
/* /*
* Find the symbol table entry and it's corresponding * Find the symbol table entry and it's corresponding
@ -179,16 +180,17 @@ __fdnlist(int fd, struct nlist *list)
goto done; goto done;
} }
/* /*
* Map string table into our address space. This gives us * Load string table into our address space. This gives us
* an easy way to randomly access all the strings, without * an easy way to randomly access all the strings, without
* making the memory allocation permanent as with malloc/free * making the memory allocation permanent as with malloc/free
* (i.e., munmap will return it to the system). * (i.e., munmap will return it to the system).
*/ */
base = mmap(NULL, (size_t)symstrsize, PROT_READ, 0, fd, strtab = malloc((size_t)symstrsize);
(off_t)symstroff); if (strtab == NULL)
if (base == MAP_FAILED) goto done;
if (pread(fd, strtab, (size_t)symstrsize, (off_t)symstroff) < 0)
goto done; goto done;
strtab = (char *)base;
/* /*
* clean out any left-over information for all valid entries. * clean out any left-over information for all valid entries.
@ -230,6 +232,7 @@ __fdnlist(int fd, struct nlist *list)
name = strtab + s->st_name; name = strtab + s->st_name;
if (name[0] == '\0') if (name[0] == '\0')
continue; continue;
for (p = list; !ISLAST(p); p++) { for (p = list; !ISLAST(p); p++) {
if ((p->n_un.n_name[0] == '_' && if ((p->n_un.n_name[0] == '_' &&
strcmp(name, p->n_un.n_name+1) == 0) strcmp(name, p->n_un.n_name+1) == 0)
@ -244,10 +247,8 @@ __fdnlist(int fd, struct nlist *list)
} }
done: done:
errsave = errno; errsave = errno;
if (strtab != NULL) free(strtab);
munmap(strtab, symstrsize); free(shdr);
if (shdr != NULL)
munmap(shdr, shdr_size);
errno = errsave; errno = errsave;
return (nent); return (nent);
} }