From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org, Mark Rutland <mark.rutland@arm.com>,
kernel-hardening@lists.openwall.com,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org,
Jeremy Linton <jeremy.linton@arm.com>,
Mark Brown <broonie@kernel.org>,
Topi Miettinen <toiwoton@gmail.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 3/6] elf: Fix failure handling in _dl_map_object_from_fd
Date: Fri, 11 Dec 2020 09:32:56 +0000 [thread overview]
Message-ID: <20201211093255.GD24625@arm.com> (raw)
In-Reply-To: <1525639f-560f-2677-b1cb-f904b3552c71@linaro.org>
The 12/10/2020 15:25, Adhemerval Zanella wrote:
> On 27/11/2020 10:20, Szabolcs Nagy via Libc-alpha wrote:
> > There are many failure paths that call lose to do local cleanups
> > in _dl_map_object_from_fd, but it did not clean everything.
> >
> > Handle l_phdr, l_libname and mapped segments in the common failure
> > handling code.
> >
> > There are various bits that may not be cleaned properly on failure
> > (e.g. executable stack, tlsid, incomplete dl_map_segments).
> > ---
> > elf/dl-load.c | 24 +++++++++++++++---------
> > 1 file changed, 15 insertions(+), 9 deletions(-)
> >
> > diff --git a/elf/dl-load.c b/elf/dl-load.c
> > index 21e55deb19..9c71b7562c 100644
> > --- a/elf/dl-load.c
> > +++ b/elf/dl-load.c
> > @@ -914,8 +914,15 @@ lose (int code, int fd, const char *name, char *realname, struct link_map *l,
> > /* The file might already be closed. */
> > if (fd != -1)
> > (void) __close_nocancel (fd);
> > + if (l != NULL && l->l_map_start != 0)
> > + _dl_unmap_segments (l);
> > if (l != NULL && l->l_origin != (char *) -1l)
> > free ((char *) l->l_origin);
> > + if (l != NULL && !l->l_libname->dont_free)
> > + free (l->l_libname);
> > + if (l != NULL && l->l_phdr_allocated)
> > + free ((void *) l->l_phdr);
> > +
> > free (l);
> > free (realname);
> >
> > @@ -1256,7 +1263,11 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> > errstring = _dl_map_segments (l, fd, header, type, loadcmds, nloadcmds,
> > maplength, has_holes, loader);
> > if (__glibc_unlikely (errstring != NULL))
> > - goto call_lose;
> > + {
> > + /* Mappings can be in an inconsistent state: avoid unmap. */
> > + l->l_map_start = l->l_map_end = 0;
> > + goto call_lose;
> > + }
> >
> > /* Process program headers again after load segments are mapped in
> > case processing requires accessing those segments. Scan program
>
> In this case I am failing to see who would be responsible to unmap
> l_map_start int the type == ET_DYN where first mmap succeeds but
> with a later mmap failure in any load command.
failures are either cleaned up locally in this function
via lose or after a clean return via dlclose.
failures that are not cleaned up will leak resources.
_dl_map_segments failure is not cleaned up (the mappings
are in an unknown state). however after a successful
_dl_map_segments later failures can clean the mappings
and that's what i fixed here.
i did not try to fix transitive design bugs (such as
leaks in _dl_map_segments) that would require interface
change or local cleanups in those other functions.
> > @@ -1294,14 +1305,6 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> > || (__glibc_unlikely (l->l_flags_1 & DF_1_PIE)
> > && __glibc_unlikely ((mode & __RTLD_OPENEXEC) == 0)))
> > {
> > - /* We are not supposed to load this object. Free all resources. */
> > - _dl_unmap_segments (l);
> > -
> > - if (!l->l_libname->dont_free)
> > - free (l->l_libname);
> > -
> > - if (l->l_phdr_allocated)
> > - free ((void *) l->l_phdr);
> >
> > if (l->l_flags_1 & DF_1_PIE)
> > errstring
> > @@ -1392,6 +1395,9 @@ cannot enable executable stack as shared object requires");
> > /* Signal that we closed the file. */
> > fd = -1;
> >
> > + /* Failures before this point are handled locally via lose.
> > + No more failures are allowed in this function until return. */
> > +
> > /* If this is ET_EXEC, we should have loaded it as lt_executable. */
> > assert (type != ET_EXEC || l->l_type == lt_executable);
> >
> >
>
> Ok.
next prev parent reply other threads:[~2020-12-11 9:33 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-27 13:19 [PATCH v2 0/6] aarch64: avoid mprotect(PROT_BTI|PROT_EXEC) [BZ #26831] Szabolcs Nagy
2020-11-27 13:19 ` [PATCH v2 1/6] aarch64: Fix missing BTI protection from dependencies [BZ #26926] Szabolcs Nagy
2020-12-10 17:51 ` Adhemerval Zanella
2020-12-11 15:33 ` Szabolcs Nagy
2020-11-27 13:20 ` [PATCH v2 2/6] elf: lose is closely tied to _dl_map_object_from_fd Szabolcs Nagy
2020-12-10 17:57 ` Adhemerval Zanella
2020-12-11 12:12 ` Szabolcs Nagy
2020-11-27 13:20 ` [PATCH v2 3/6] elf: Fix failure handling in _dl_map_object_from_fd Szabolcs Nagy
2020-12-10 18:25 ` Adhemerval Zanella
2020-12-11 9:32 ` Szabolcs Nagy [this message]
2020-11-27 13:20 ` [PATCH v2 4/6] elf: Move note processing after l_phdr is updated Szabolcs Nagy
2020-12-10 18:30 ` Adhemerval Zanella
2020-11-27 13:21 ` [PATCH v2 5/6] elf: Pass the fd to note processing Szabolcs Nagy
2020-12-10 18:35 ` Adhemerval Zanella
2020-11-27 13:21 ` [PATCH v2 6/6] aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Szabolcs Nagy
2020-12-02 8:55 ` [PATCH v3 1/2] aarch64: align address for BTI protection [BZ #26988] Szabolcs Nagy
2020-12-10 18:49 ` Adhemerval Zanella
2020-12-02 8:55 ` [PATCH v3 2/2] aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Szabolcs Nagy
2020-12-10 19:12 ` Adhemerval Zanella
2020-11-30 15:56 ` [PATCH v2 0/6] aarch64: avoid mprotect(PROT_BTI|PROT_EXEC) " Szabolcs Nagy
2020-12-03 17:30 ` Catalin Marinas
2020-12-07 20:03 ` Szabolcs Nagy
2020-12-11 17:46 ` Catalin Marinas
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=20201211093255.GD24625@arm.com \
--to=szabolcs.nagy@arm.com \
--cc=adhemerval.zanella@linaro.org \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=jeremy.linton@arm.com \
--cc=kernel-hardening@lists.openwall.com \
--cc=libc-alpha@sourceware.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=toiwoton@gmail.com \
--cc=will@kernel.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).