From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Sergey Bugaev <bugaevc@gmail.com>,
libc-alpha@sourceware.org, Florian Weimer <fweimer@redhat.com>
Cc: bug-hurd@gnu.org
Subject: Re: [RFC PATCH 1/2] elf: Port ldconfig away from stack-allocated paths
Date: Tue, 23 May 2023 14:57:43 -0300 [thread overview]
Message-ID: <4163e51f-f983-d1a1-20e3-3ef2ae38fcde@linaro.org> (raw)
In-Reply-To: <20230520190306.4008296-1-bugaevc@gmail.com>
On 20/05/23 16:03, Sergey Bugaev wrote:
> Hello,
>
> On Fri, May 19, 2023 at 3:25 PM Florian Weimer <fweimer@redhat.com> wrote:
>> Missing error checking?
>
> Indeed, thanks. Fixed.
>
>> I think we use x* functions such a xstrdup elsewhere in ldconfig, so you
>> could add xasprintf as well.
>
> Apparently the existing code didn't #include <support/support.h> and link
> to libsupport (xstrdup must be coming from somewhere else.) I opted to
> check for asprintf returning < 0 and calling error () explicitly instead,
> like other code in this same file does already.
>
> Sergey
>
> -- >8 --
> Subject: [PATCH 1/2 v2] 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>
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Still looks good to me, thanks.
> ---
> elf/ldconfig.c | 60 +++++++++++++++++++-------------------------------
> 1 file changed, 23 insertions(+), 37 deletions(-)
>
> diff --git a/elf/ldconfig.c b/elf/ldconfig.c
> index 2fc45ad8..e643dd57 100644
> --- a/elf/ldconfig.c
> +++ b/elf/ldconfig.c
> @@ -677,28 +677,18 @@ search_dir (const struct dir_entry *entry)
>
> char *dir_name;
> char *real_file_name;
> - size_t real_file_name_len;
> - size_t file_name_len = PATH_MAX;
> - char *file_name = alloca (file_name_len);
> + char *file_name;
> if (opt_chroot != NULL)
> - {
> - dir_name = chroot_canon (opt_chroot, entry->path);
> - real_file_name_len = PATH_MAX;
> - real_file_name = alloca (real_file_name_len);
> - }
> + dir_name = chroot_canon (opt_chroot, entry->path);
> else
> - {
> - dir_name = entry->path;
> - real_file_name_len = 0;
> - real_file_name = file_name;
> - }
> + dir_name = entry->path;
>
> DIR *dir;
> if (dir_name == NULL || (dir = opendir (dir_name)) == NULL)
> {
> if (opt_verbose)
> error (0, errno, _("Can't open directory %s"), entry->path);
> - if (opt_chroot != NULL && dir_name != NULL)
> + if (opt_chroot != NULL)
> free (dir_name);
> return;
> }
> @@ -733,25 +723,16 @@ search_dir (const struct dir_entry *entry)
> + 1, ".#prelink#.", sizeof (".#prelink#.") - 1) == 0)
> continue;
> }
> - len += strlen (entry->path) + 2;
> - if (len > file_name_len)
> - {
> - 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 (asprintf (&file_name, "%s/%s", entry->path, direntry->d_name) < 0)
> + error (EXIT_FAILURE, errno, _("Could not form library path"));
> if (opt_chroot != NULL)
> {
> - len = strlen (dir_name) + strlen (direntry->d_name) + 2;
> - if (len > real_file_name_len)
> - {
> - real_file_name_len = len;
> - real_file_name = alloca (real_file_name_len);
> - }
> - sprintf (real_file_name, "%s/%s", dir_name, direntry->d_name);
> + if (asprintf (&real_file_name, "%s/%s",
> + dir_name, direntry->d_name) < 0)
> + error (EXIT_FAILURE, errno, _("Could not form library path"));
> }
> + else
> + real_file_name = file_name;
>
> struct stat lstat_buf;
> /* 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)))
> {
> error (0, errno, _("Cannot lstat %s"), file_name);
> - continue;
> + goto next;
> }
>
> struct stat stat_buf;
> @@ -778,7 +759,7 @@ search_dir (const struct dir_entry *entry)
> {
> if (strstr (file_name, ".so") == NULL)
> error (0, 0, _("Input file %s not found.\n"), file_name);
> - continue;
> + goto next;
> }
> }
> if (__glibc_unlikely (stat (target_name, &stat_buf)))
> @@ -793,7 +774,7 @@ search_dir (const struct dir_entry *entry)
> if (opt_chroot != NULL)
> free (target_name);
>
> - continue;
> + goto next;
> }
>
> if (opt_chroot != NULL)
> @@ -806,7 +787,7 @@ search_dir (const struct dir_entry *entry)
> lstat_buf.st_ctime = stat_buf.st_ctime;
> }
> else if (!S_ISREG (lstat_buf.st_mode))
> - continue;
> + goto next;
>
> char *real_name;
> if (opt_chroot != NULL && is_link)
> @@ -816,7 +797,7 @@ search_dir (const struct dir_entry *entry)
> {
> if (strstr (file_name, ".so") == NULL)
> error (0, 0, _("Input file %s not found.\n"), file_name);
> - continue;
> + goto next;
> }
> }
> else
> @@ -828,7 +809,7 @@ search_dir (const struct dir_entry *entry)
> && __builtin_expect (lstat (real_file_name, &lstat_buf), 0))
> {
> error (0, errno, _("Cannot lstat %s"), file_name);
> - continue;
> + goto next;
> }
>
> /* 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)
> free (real_name);
> - continue;
> + goto next;
> }
> else if (opt_build_cache)
> add_to_aux_cache (&lstat_buf, flag, isa_level, soname);
> @@ -948,6 +929,11 @@ search_dir (const struct dir_entry *entry)
> dlib_ptr->next = dlibs;
> dlibs = dlib_ptr;
> }
> +
> + next:
> + free (file_name);
> + if (opt_chroot != NULL)
> + free (real_file_name);
> }
>
> closedir (dir);
next prev parent reply other threads:[~2023-05-23 17:57 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 18:54 [RFC PATCH 0/2] On ldconfig and ld.so.cache Sergey Bugaev
2023-05-17 18:54 ` [RFC PATCH 1/2] elf: Port ldconfig away from stack-allocated paths Sergey Bugaev
2023-05-18 19:13 ` Adhemerval Zanella Netto
2023-05-19 12:25 ` Florian Weimer
2023-05-20 19:03 ` Sergey Bugaev
2023-05-23 17:57 ` Adhemerval Zanella Netto [this message]
2023-05-25 8:07 ` Florian Weimer
2023-05-17 18:54 ` [RFC PATCH 2/2] x86: Make dl-cache.h and readelflib.c not Linux-specific Sergey Bugaev
2023-05-19 11:36 ` Carlos O'Donell
2023-05-19 11:52 ` [RFC PATCH 0/2] On ldconfig and ld.so.cache Carlos O'Donell
2023-05-19 12:30 ` Florian Weimer
2023-05-19 13:21 ` Sergey Bugaev
2023-05-24 14:09 ` Ludovic Courtès
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4163e51f-f983-d1a1-20e3-3ef2ae38fcde@linaro.org \
--to=adhemerval.zanella@linaro.org \
--cc=bug-hurd@gnu.org \
--cc=bugaevc@gmail.com \
--cc=fweimer@redhat.com \
--cc=libc-alpha@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).