Re: [PATCH v2 3/6] elf: Fix failure handling in _dl_map_object_from_fd
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.
Re: [PATCH v2 3/6] elf: Fix failure handling in _dl_map_object_from_fd
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.
> @@ -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.
[PATCH v2 3/6] elf: Fix failure handling in _dl_map_object_from_fd
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
@@ -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);
--
2.17.1
