[RFC,v8,16/20] Suppress inter-namespace DSO sharing for audit libraries
Commit Message
Audit libraries should not participate in DSO sharing: In
particular libraries tagged with DF_GNU_1_UNIQUE should not
be shared between the audit namespace and any others - they
should get their own copy.
This is signalled to the loader code by passing the RTLD_ISOLATE
flag from the relevant entry point in the dl modes argument.
---
bits/dlfcn.h | 3 +++
elf/dl-load.c | 5 +++--
elf/dl-open.c | 13 +++++++++++--
elf/rtld.c | 2 +-
sysdeps/mips/bits/dlfcn.h | 3 +++
5 files changed, 21 insertions(+), 5 deletions(-)
Comments
On 09/02/2021 14:18, Vivek Das Mohapatra via Libc-alpha wrote:
> Audit libraries should not participate in DSO sharing: In
> particular libraries tagged with DF_GNU_1_UNIQUE should not
> be shared between the audit namespace and any others - they
> should get their own copy.
>
> This is signalled to the loader code by passing the RTLD_ISOLATE
> flag from the relevant entry point in the dl modes argument.
> ---
> bits/dlfcn.h | 3 +++
> elf/dl-load.c | 5 +++--
> elf/dl-open.c | 13 +++++++++++--
> elf/rtld.c | 2 +-
> sysdeps/mips/bits/dlfcn.h | 3 +++
> 5 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/bits/dlfcn.h b/bits/dlfcn.h
> index 0daa789693..f910528b32 100644
> --- a/bits/dlfcn.h
> +++ b/bits/dlfcn.h
> @@ -32,6 +32,9 @@
> visible as if the object were linked directly into the program. */
> #define RTLD_GLOBAL 0x00100
>
> +/* Suppress RTLD_SHARED and/or DF_GNU_1_UNIQUE. */
> +#define RTLD_ISOLATE 0x00040
> +
> /* If the following bit is set in the MODE argument to dlmopen
> then the target object is loaded into the main namespace (if
> it is not already there) and a shallow copy (proxy) is placed
Ok, the idea is to export the new flag to userpace.
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index 4e8e7ca031..44fd3b5489 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -1079,7 +1079,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> /* DSOs in the main namespace which are flagged DF_GNU_1_UNIQUE should only
> be opened into the main namespace. Other namespaces should only get
> proxies. */
> - if (__glibc_unlikely (nsid != LM_ID_BASE))
> + if (__glibc_unlikely ((nsid != LM_ID_BASE) && !(mode & RTLD_ISOLATE)))
> {
> /* Check base ns to see if the name matched another already loaded. */
> for (l = GL(dl_ns)[LM_ID_BASE]._ns_loaded; l != NULL; l = l->l_next)
> @@ -1174,7 +1174,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>
> /* We need to check for DT_GNU_FLAGS_1/DF_GNU_1_UNIQUE before we start
> initialising any namespace dependent metatada. */
> - if (nsid != LM_ID_BASE)
> + if (__glibc_unlikely ((nsid != LM_ID_BASE) && !(mode & RTLD_ISOLATE)))
> {
> /* Target DSO is flagged as unique: Make sure it gets loaded into
> the base namespace. It is up to our caller to generate a proxy in
Ok.
> @@ -2188,6 +2188,7 @@ _dl_map_object (struct link_map *loader, const char *name,
>
> assert (nsid >= 0);
> assert (nsid < GL(dl_nns));
> + assert (!((mode & RTLD_ISOLATE) && (mode & RTLD_SHARED)));
>
> #ifdef SHARED
> /* Only need to do proxy checks if `nsid' is not LM_ID_BASE. */
> diff --git a/elf/dl-open.c b/elf/dl-open.c
> index 38b3587d4a..d3c3e32be2 100644
> --- a/elf/dl-open.c
> +++ b/elf/dl-open.c
> @@ -485,9 +485,16 @@ dl_open_worker (void *a)
> int mode = args->mode;
> struct link_map *call_map = NULL;
> struct link_map *preloaded = NULL;
> - int want_proxy = mode & RTLD_SHARED;
> + int want_proxy = 0;
> + int dl_isolate = mode & RTLD_ISOLATE;
Use 'bool' here.
> Lmid_t proxy_ns = LM_ID_BASE;
>
> + /* Isolation means we should suppress all inter-namespace sharing. */
> + if (dl_isolate)
> + mode &= ~RTLD_SHARED;
> + else
> + want_proxy = mode & RTLD_SHARED;
> +
Indentation seems off here (4 space instead of 2).
> /* Determine the caller's map if necessary. This is needed in case
> we have a DST, when we don't know the namespace ID we have to put
> the new object in, or when the file name has no path in which
> @@ -539,6 +546,7 @@ dl_open_worker (void *a)
> mode and set want_proxy.
> NOTE: RTLD_ISOLATE in the mode suppresses this behaviour. */
> if (__glibc_unlikely (args->nsid != LM_ID_BASE) &&
> + __glibc_likely (!dl_isolate) &&
> __glibc_likely (!want_proxy))
> {
> preloaded = _dl_find_dso (file, LM_ID_BASE);
> @@ -650,7 +658,8 @@ dl_open_worker (void *a)
>
> /* Load that object's dependencies. */
> _dl_map_object_deps (new, NULL, 0, 0,
> - mode & (__RTLD_DLOPEN | RTLD_DEEPBIND | __RTLD_AUDIT));
> + mode & (__RTLD_DLOPEN | RTLD_DEEPBIND | __RTLD_AUDIT |
> + RTLD_ISOLATE));
>
> /* So far, so good. Now check the versions. */
Ok.
> for (unsigned int i = 0; i < new->l_searchlist.r_nlist; ++i)
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 596b6ac3d9..82069658b3 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -659,7 +659,7 @@ dlmopen_doit (void *a)
> struct dlmopen_args *args = (struct dlmopen_args *) a;
> args->map = _dl_open (args->fname,
> (RTLD_LAZY | __RTLD_DLOPEN | __RTLD_AUDIT
> - | __RTLD_SECURE),
> + | __RTLD_SECURE | RTLD_ISOLATE),
> dl_main, LM_ID_NEWLM, _dl_argc, _dl_argv,
> __environ);
> }
> diff --git a/sysdeps/mips/bits/dlfcn.h b/sysdeps/mips/bits/dlfcn.h
> index 1331771a17..a0a35bba5d 100644
> --- a/sysdeps/mips/bits/dlfcn.h
> +++ b/sysdeps/mips/bits/dlfcn.h
> @@ -39,6 +39,9 @@
> share a single instance of a DSO. */
> #define RTLD_SHARED 0x00020
>
> +/* Suppress RTLD_SHARED and/or DF_GNU_1_UNIQUE. */
> +#define RTLD_ISOLATE 0x00040
> +
> /* Unix98 demands the following flag which is the inverse to RTLD_GLOBAL.
> The implementation does this by default and so we can define the
> value to zero. */
>
Ok.
@@ -32,6 +32,9 @@
visible as if the object were linked directly into the program. */
#define RTLD_GLOBAL 0x00100
+/* Suppress RTLD_SHARED and/or DF_GNU_1_UNIQUE. */
+#define RTLD_ISOLATE 0x00040
+
/* If the following bit is set in the MODE argument to dlmopen
then the target object is loaded into the main namespace (if
it is not already there) and a shallow copy (proxy) is placed
@@ -1079,7 +1079,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
/* DSOs in the main namespace which are flagged DF_GNU_1_UNIQUE should only
be opened into the main namespace. Other namespaces should only get
proxies. */
- if (__glibc_unlikely (nsid != LM_ID_BASE))
+ if (__glibc_unlikely ((nsid != LM_ID_BASE) && !(mode & RTLD_ISOLATE)))
{
/* Check base ns to see if the name matched another already loaded. */
for (l = GL(dl_ns)[LM_ID_BASE]._ns_loaded; l != NULL; l = l->l_next)
@@ -1174,7 +1174,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
/* We need to check for DT_GNU_FLAGS_1/DF_GNU_1_UNIQUE before we start
initialising any namespace dependent metatada. */
- if (nsid != LM_ID_BASE)
+ if (__glibc_unlikely ((nsid != LM_ID_BASE) && !(mode & RTLD_ISOLATE)))
{
/* Target DSO is flagged as unique: Make sure it gets loaded into
the base namespace. It is up to our caller to generate a proxy in
@@ -2188,6 +2188,7 @@ _dl_map_object (struct link_map *loader, const char *name,
assert (nsid >= 0);
assert (nsid < GL(dl_nns));
+ assert (!((mode & RTLD_ISOLATE) && (mode & RTLD_SHARED)));
#ifdef SHARED
/* Only need to do proxy checks if `nsid' is not LM_ID_BASE. */
@@ -485,9 +485,16 @@ dl_open_worker (void *a)
int mode = args->mode;
struct link_map *call_map = NULL;
struct link_map *preloaded = NULL;
- int want_proxy = mode & RTLD_SHARED;
+ int want_proxy = 0;
+ int dl_isolate = mode & RTLD_ISOLATE;
Lmid_t proxy_ns = LM_ID_BASE;
+ /* Isolation means we should suppress all inter-namespace sharing. */
+ if (dl_isolate)
+ mode &= ~RTLD_SHARED;
+ else
+ want_proxy = mode & RTLD_SHARED;
+
/* Determine the caller's map if necessary. This is needed in case
we have a DST, when we don't know the namespace ID we have to put
the new object in, or when the file name has no path in which
@@ -539,6 +546,7 @@ dl_open_worker (void *a)
mode and set want_proxy.
NOTE: RTLD_ISOLATE in the mode suppresses this behaviour. */
if (__glibc_unlikely (args->nsid != LM_ID_BASE) &&
+ __glibc_likely (!dl_isolate) &&
__glibc_likely (!want_proxy))
{
preloaded = _dl_find_dso (file, LM_ID_BASE);
@@ -650,7 +658,8 @@ dl_open_worker (void *a)
/* Load that object's dependencies. */
_dl_map_object_deps (new, NULL, 0, 0,
- mode & (__RTLD_DLOPEN | RTLD_DEEPBIND | __RTLD_AUDIT));
+ mode & (__RTLD_DLOPEN | RTLD_DEEPBIND | __RTLD_AUDIT |
+ RTLD_ISOLATE));
/* So far, so good. Now check the versions. */
for (unsigned int i = 0; i < new->l_searchlist.r_nlist; ++i)
@@ -659,7 +659,7 @@ dlmopen_doit (void *a)
struct dlmopen_args *args = (struct dlmopen_args *) a;
args->map = _dl_open (args->fname,
(RTLD_LAZY | __RTLD_DLOPEN | __RTLD_AUDIT
- | __RTLD_SECURE),
+ | __RTLD_SECURE | RTLD_ISOLATE),
dl_main, LM_ID_NEWLM, _dl_argc, _dl_argv,
__environ);
}
@@ -39,6 +39,9 @@
share a single instance of a DSO. */
#define RTLD_SHARED 0x00020
+/* Suppress RTLD_SHARED and/or DF_GNU_1_UNIQUE. */
+#define RTLD_ISOLATE 0x00040
+
/* Unix98 demands the following flag which is the inverse to RTLD_GLOBAL.
The implementation does this by default and so we can define the
value to zero. */