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elf: Port ldconfig away from stack-allocated paths 

ldconfig was allocating PATH_MAX bytes on the stack for the library file
name. The issues with PATH_MAX usage are well documented [0][1]; even if
a program does not rely on paths being limited to PATH_MAX bytes,
allocating 4096 bytes on the stack for paths that are typically rather
short (strlen ("/lib64/libc.so.6") is 16) is wasteful and dangerous.

[0]: https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
[1]: https://eklitzke.org/path-max-is-tricky

Instead, make use of asprintf to dynamically allocate memory of just the
right size on the heap.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
This commit is contained in:
Sergey Bugaev 2023-06-17 19:40:25 +03:00 committed by Adhemerval Zanella
parent 21fbc0a193
commit daf7b53a3c
1 changed files with 22 additions and 37 deletions
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59
elf/ldconfig.c
View File

@ -677,28 +677,18 @@ search_dir (const struct dir_entry *entry)
char *dir_name; char *dir_name;
char *real_file_name; char *real_file_name;
size_t real_file_name_len; char *file_name;
size_t file_name_len = PATH_MAX;
char *file_name = alloca (file_name_len);
if (opt_chroot != NULL) if (opt_chroot != NULL)
{ dir_name = chroot_canon (opt_chroot, entry->path);
dir_name = chroot_canon (opt_chroot, entry->path);
real_file_name_len = PATH_MAX;
real_file_name = alloca (real_file_name_len);
}
else else
{ dir_name = entry->path;
dir_name = entry->path;
real_file_name_len = 0;
real_file_name = file_name;
}
DIR *dir; DIR *dir;
if (dir_name == NULL || (dir = opendir (dir_name)) == NULL) if (dir_name == NULL || (dir = opendir (dir_name)) == NULL)
{ {
if (opt_verbose) if (opt_verbose)
error (0, errno, _("Can't open directory %s"), entry->path); error (0, errno, _("Can't open directory %s"), entry->path);
if (opt_chroot != NULL && dir_name != NULL) if (opt_chroot != NULL)
free (dir_name); free (dir_name);
return; return;
} }
@ -733,25 +723,16 @@ search_dir (const struct dir_entry *entry)
+ 1, ".#prelink#.", sizeof (".#prelink#.") - 1) == 0) + 1, ".#prelink#.", sizeof (".#prelink#.") - 1) == 0)
continue; continue;
} }
len += strlen (entry->path) + 2; if (asprintf (&file_name, "%s/%s", entry->path, direntry->d_name) < 0)
if (len > file_name_len) error (EXIT_FAILURE, errno, _("Could not form library path"));
{
file_name_len = len;
file_name = alloca (file_name_len);
if (!opt_chroot)
real_file_name = file_name;
}
sprintf (file_name, "%s/%s", entry->path, direntry->d_name);
if (opt_chroot != NULL) if (opt_chroot != NULL)
{ {
len = strlen (dir_name) + strlen (direntry->d_name) + 2; if (asprintf (&real_file_name, "%s/%s",
if (len > real_file_name_len) dir_name, direntry->d_name) < 0)
{ error (EXIT_FAILURE, errno, _("Could not form library path"));
real_file_name_len = len;
real_file_name = alloca (real_file_name_len);
}
sprintf (real_file_name, "%s/%s", dir_name, direntry->d_name);
} }
else
real_file_name = xstrdup (file_name);
struct stat lstat_buf; struct stat lstat_buf;
/* We optimize and try to do the lstat call only if needed. */ /* We optimize and try to do the lstat call only if needed. */
@ -761,7 +742,7 @@ search_dir (const struct dir_entry *entry)
if (__glibc_unlikely (lstat (real_file_name, &lstat_buf))) if (__glibc_unlikely (lstat (real_file_name, &lstat_buf)))
{ {
error (0, errno, _("Cannot lstat %s"), file_name); error (0, errno, _("Cannot lstat %s"), file_name);
continue; goto next;
} }
struct stat stat_buf; struct stat stat_buf;
@ -778,7 +759,7 @@ search_dir (const struct dir_entry *entry)
{ {
if (strstr (file_name, ".so") == NULL) if (strstr (file_name, ".so") == NULL)
error (0, 0, _("Input file %s not found.\n"), file_name); error (0, 0, _("Input file %s not found.\n"), file_name);
continue; goto next;
} }
} }
if (__glibc_unlikely (stat (target_name, &stat_buf))) if (__glibc_unlikely (stat (target_name, &stat_buf)))
@ -793,7 +774,7 @@ search_dir (const struct dir_entry *entry)
if (opt_chroot != NULL) if (opt_chroot != NULL)
free (target_name); free (target_name);
continue; goto next;
} }
if (opt_chroot != NULL) if (opt_chroot != NULL)
@ -806,7 +787,7 @@ search_dir (const struct dir_entry *entry)
lstat_buf.st_ctime = stat_buf.st_ctime; lstat_buf.st_ctime = stat_buf.st_ctime;
} }
else if (!S_ISREG (lstat_buf.st_mode)) else if (!S_ISREG (lstat_buf.st_mode))
continue; goto next;
char *real_name; char *real_name;
if (opt_chroot != NULL && is_link) if (opt_chroot != NULL && is_link)
@ -816,7 +797,7 @@ search_dir (const struct dir_entry *entry)
{ {
if (strstr (file_name, ".so") == NULL) if (strstr (file_name, ".so") == NULL)
error (0, 0, _("Input file %s not found.\n"), file_name); error (0, 0, _("Input file %s not found.\n"), file_name);
continue; goto next;
} }
} }
else else
@ -828,7 +809,7 @@ search_dir (const struct dir_entry *entry)
&& __builtin_expect (lstat (real_file_name, &lstat_buf), 0)) && __builtin_expect (lstat (real_file_name, &lstat_buf), 0))
{ {
error (0, errno, _("Cannot lstat %s"), file_name); error (0, errno, _("Cannot lstat %s"), file_name);
continue; goto next;
} }
/* First search whether the auxiliary cache contains this /* First search whether the auxiliary cache contains this
@ -842,7 +823,7 @@ search_dir (const struct dir_entry *entry)
{ {
if (real_name != real_file_name) if (real_name != real_file_name)
free (real_name); free (real_name);
continue; goto next;
} }
else if (opt_build_cache) else if (opt_build_cache)
add_to_aux_cache (&lstat_buf, flag, isa_level, soname); add_to_aux_cache (&lstat_buf, flag, isa_level, soname);
@ -948,6 +929,10 @@ search_dir (const struct dir_entry *entry)
dlib_ptr->next = dlibs; dlib_ptr->next = dlibs;
dlibs = dlib_ptr; dlibs = dlib_ptr;
} }
next:
free (file_name);
free (real_file_name);
} }
closedir (dir); closedir (dir);