From db3476aff19b75c4fdefbe65fcd5f0a90588ba51 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Thu, 23 Jun 2016 20:01:40 +0200 Subject: 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. --- libio/fileops.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) (limited to 'libio/fileops.c') diff --git a/libio/fileops.c b/libio/fileops.c index 8e83b1cd7b..1315735427 100644 --- a/libio/fileops.c +++ b/libio/fileops.c @@ -140,7 +140,7 @@ extern struct __gconv_trans_data __libio_translit attribute_hidden; void -_IO_new_file_init (struct _IO_FILE_plus *fp) +_IO_new_file_init_internal (struct _IO_FILE_plus *fp) { /* POSIX.1 allows another file handle to be used to change the position of our file descriptor. Hence we actually don't know the actual @@ -151,7 +151,15 @@ _IO_new_file_init (struct _IO_FILE_plus *fp) _IO_link_in (fp); fp->file._fileno = -1; } -libc_hidden_ver (_IO_new_file_init, _IO_file_init) + +/* External version of _IO_new_file_init_internal which switches off + vtable validation. */ +void +_IO_new_file_init (struct _IO_FILE_plus *fp) +{ + IO_set_accept_foreign_vtables (&_IO_vtable_check); + _IO_new_file_init_internal (fp); +} int _IO_new_file_close_it (_IO_FILE *fp) @@ -1534,7 +1542,7 @@ versioned_symbol (libc, _IO_new_file_write, _IO_file_write, GLIBC_2_1); versioned_symbol (libc, _IO_new_file_xsputn, _IO_file_xsputn, GLIBC_2_1); #endif -const struct _IO_jump_t _IO_file_jumps = +const struct _IO_jump_t _IO_file_jumps libio_vtable = { JUMP_INIT_DUMMY, JUMP_INIT(finish, _IO_file_finish), @@ -1559,7 +1567,7 @@ const struct _IO_jump_t _IO_file_jumps = }; libc_hidden_data_def (_IO_file_jumps) -const struct _IO_jump_t _IO_file_jumps_mmap = +const struct _IO_jump_t _IO_file_jumps_mmap libio_vtable = { JUMP_INIT_DUMMY, JUMP_INIT(finish, _IO_file_finish), @@ -1583,7 +1591,7 @@ const struct _IO_jump_t _IO_file_jumps_mmap = JUMP_INIT(imbue, _IO_default_imbue) }; -const struct _IO_jump_t _IO_file_jumps_maybe_mmap = +const struct _IO_jump_t _IO_file_jumps_maybe_mmap libio_vtable = { JUMP_INIT_DUMMY, JUMP_INIT(finish, _IO_file_finish), -- cgit 1.4.1