There are various sanity checks that depend on knowing the file size of the underlying ELF file which we only used when mmapping the ELF file. Although we probably won't crash if we use pread to try to read from the file, we still might return completely bogus data structures. This could cause us to malloc insane amounts of memory.
Always try to get the maxsize when unknown in elf_begin.c (read_file). https://bugzilla.redhat.com/show_bug.cgi?id=1388057 Signed-off-by: Mark Wielaard <[email protected]> --- libelf/ChangeLog | 8 ++++++-- libelf/elf_begin.c | 37 +++++++++++++++++++++---------------- 2 files changed, 27 insertions(+), 18 deletions(-) diff --git a/libelf/ChangeLog b/libelf/ChangeLog index 35af786..39fbccf 100644 --- a/libelf/ChangeLog +++ b/libelf/ChangeLog @@ -1,4 +1,8 @@ -2015-10-11 Akihiko Odaki <[email protected]> +2016-10-26 Mark Wielaard <[email protected]> + + * elf_begin.c (read_file): Always set maxsize when parent == NULL. + +2016-10-11 Akihiko Odaki <[email protected]> * elf_getarsym.c (elf_getarsym): Open code rawmemchr when not available. @@ -6,7 +10,7 @@ (validate_str): New function. (elf_strptr): Use validate_str instead of memrchr. -2015-10-11 Akihiko Odaki <[email protected]> +2016-10-11 Akihiko Odaki <[email protected]> * elf32_updatefile.c: Remove sys/param.h include. * elf32_updatenull.c: Likewise. Add system.h include. diff --git a/libelf/elf_begin.c b/libelf/elf_begin.c index 8fdb376..5e9099c 100644 --- a/libelf/elf_begin.c +++ b/libelf/elf_begin.c @@ -1,5 +1,5 @@ /* Create descriptor for processing file. - Copyright (C) 1998-2010, 2012, 2014, 2015 Red Hat, Inc. + Copyright (C) 1998-2010, 2012, 2014, 2015, 2016 Red Hat, Inc. This file is part of elfutils. Written by Ulrich Drepper <[email protected]>, 1998. @@ -605,22 +605,30 @@ read_file (int fildes, off_t offset, size_t maxsize, || cmd == ELF_C_WRITE_MMAP || cmd == ELF_C_READ_MMAP_PRIVATE); + if (parent == NULL) + { + if (maxsize == ~((size_t) 0)) + { + /* We don't know in the moment how large the file is. + Determine it now. */ + struct stat st; + + if (fstat (fildes, &st) == 0 + && (sizeof (size_t) >= sizeof (st.st_size) + || st.st_size <= ~((size_t) 0))) + maxsize = (size_t) st.st_size; + } + } + else + { + /* The parent is already loaded. Use it. */ + assert (maxsize != ~((size_t) 0)); + } + if (use_mmap) { if (parent == NULL) { - if (maxsize == ~((size_t) 0)) - { - /* We don't know in the moment how large the file is. - Determine it now. */ - struct stat st; - - if (fstat (fildes, &st) == 0 - && (sizeof (size_t) >= sizeof (st.st_size) - || st.st_size <= ~((size_t) 0))) - maxsize = (size_t) st.st_size; - } - /* We try to map the file ourself. */ map_address = mmap (NULL, maxsize, (cmd == ELF_C_READ_MMAP ? PROT_READ @@ -635,9 +643,6 @@ read_file (int fildes, off_t offset, size_t maxsize, } else { - /* The parent is already loaded. Use it. */ - assert (maxsize != ~((size_t) 0)); - map_address = parent->map_address; } } -- 1.8.3.1 _______________________________________________ elfutils-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
