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authorFlorian Weimer <fweimer@redhat.com>2016-06-23 20:01:40 +0200
committerFlorian Weimer <fweimer@redhat.com>2016-06-23 20:01:52 +0200
commitdb3476aff19b75c4fdefbe65fcd5f0a90588ba51 (patch)
tree5cefd4971a0e6b5d5f9eacf6d3532c6aedc7b352 /stdio-common
parent64ba17317dc9343f0958755ad04af71ec3da637b (diff)
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libio: Implement vtable verification [BZ #20191]
This commit puts all libio vtables in a dedicated, read-only ELF section, so that they are consecutive in memory. Before any indirect jump, the vtable pointer is checked against the section boundaries, and the process is terminated if the vtable pointer does not fall into the special ELF section. To enable backwards compatibility, a special flag variable (_IO_accept_foreign_vtables), protected by the pointer guard, avoids process termination if libio stream object constructor functions have been called earlier. Such constructor functions are called by the GCC 2.95 libstdc++ library, and this mechanism ensures compatibility with old binaries. Existing callers inside glibc of these functions are adjusted to call the original functions, not the wrappers which enable vtable compatiblity. The compatibility mechanism is used to enable passing FILE * objects across a static dlopen boundary, too.
Diffstat (limited to 'stdio-common')
-rw-r--r--stdio-common/vfprintf.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/stdio-common/vfprintf.c b/stdio-common/vfprintf.c
index f24020a..6e428e9 100644
--- a/stdio-common/vfprintf.c
+++ b/stdio-common/vfprintf.c
@@ -2240,7 +2240,7 @@ _IO_helper_overflow (_IO_FILE *s, int c)
}
#ifdef COMPILE_WPRINTF
-static const struct _IO_jump_t _IO_helper_jumps =
+static const struct _IO_jump_t _IO_helper_jumps libio_vtable =
{
JUMP_INIT_DUMMY,
JUMP_INIT (finish, _IO_wdefault_finish),
@@ -2262,7 +2262,7 @@ static const struct _IO_jump_t _IO_helper_jumps =
JUMP_INIT (stat, _IO_default_stat)
};
#else
-static const struct _IO_jump_t _IO_helper_jumps =
+static const struct _IO_jump_t _IO_helper_jumps libio_vtable =
{
JUMP_INIT_DUMMY,
JUMP_INIT (finish, _IO_default_finish),