Commit 47013bc92a1d0f71477aa018068b0923fdaf6ccf
2017-06-14T01:49:25
Fix broken mmap() usage in nlist() by switching to pread() 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.
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diff --git a/src/nlist.c b/src/nlist.c
index e5dede0..0932f59 100644
--- a/src/nlist.c
+++ b/src/nlist.c
@@ -36,6 +36,7 @@
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
+#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <nlist.h>
@@ -131,7 +132,6 @@ __fdnlist(int fd, struct nlist *list)
char *strtab = NULL;
Elf_Shdr *shdr = NULL;
Elf_Word shdr_size;
- void *base;
struct stat st;
/* Make sure obj is OK */
@@ -150,12 +150,13 @@ __fdnlist(int fd, struct nlist *list)
return (-1);
}
- /* mmap section header table */
- base = mmap(NULL, (size_t)shdr_size, PROT_READ, 0, fd,
- (off_t)ehdr.e_shoff);
- if (base == MAP_FAILED)
+ shdr = malloc((size_t)shdr_size);
+ if (shdr == NULL)
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
@@ -179,16 +180,17 @@ __fdnlist(int fd, struct nlist *list)
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
* making the memory allocation permanent as with malloc/free
* (i.e., munmap will return it to the system).
*/
- base = mmap(NULL, (size_t)symstrsize, PROT_READ, 0, fd,
- (off_t)symstroff);
- if (base == MAP_FAILED)
+ strtab = malloc((size_t)symstrsize);
+ if (strtab == NULL)
+ goto done;
+
+ if (pread(fd, strtab, (size_t)symstrsize, (off_t)symstroff) < 0)
goto done;
- strtab = (char *)base;
/*
* 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;
if (name[0] == '\0')
continue;
+
for (p = list; !ISLAST(p); p++) {
if ((p->n_un.n_name[0] == '_' &&
strcmp(name, p->n_un.n_name+1) == 0)
@@ -244,10 +247,8 @@ __fdnlist(int fd, struct nlist *list)
}
done:
errsave = errno;
- if (strtab != NULL)
- munmap(strtab, symstrsize);
- if (shdr != NULL)
- munmap(shdr, shdr_size);
+ free(strtab);
+ free(shdr);
errno = errsave;
return (nent);
}