Traditionally, only the final PT_LOAD for load_elf_interp() supported having p_memsz > p_filesz. Recently, lld's construction of musl's libc.so on PowerPC64 started having two PT_LOAD program headers with p_memsz > p_filesz. As the least invasive change possible, check for p_memsz > p_filesz for each PT_LOAD in load_elf_interp. Reported-by: Rich Felker <dalias@xxxxxxxx> Link: https://maskray.me/blog/2022-11-05-lld-musl-powerpc64 Cc: Pedro Falcato <pedro.falcato@xxxxxxxxx> Cc: Fangrui Song <maskray@xxxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- Rich, Pedro, and Fangrui, are you able to test this change? I haven't constructed a trivial reproducer yet (though it would be nice to have a self-contained test-case). --- fs/binfmt_elf.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 528e2ac8931f..3f07945ff085 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -673,18 +673,19 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, last_bss = k; bss_prot = elf_prot; } + + /* + * Now fill out any zeroed region (e.g. .bss): first pad the + * last page from the file up to the page boundary, and zero + * it from elf_bss up to the end of the page. + */ + if (last_bss > elf_bss && padzero(elf_bss)) { + error = -EFAULT; + goto out; + } } } - /* - * Now fill out the bss section: first pad the last page from - * the file up to the page boundary, and zero it from elf_bss - * up to the end of the page. - */ - if (padzero(elf_bss)) { - error = -EFAULT; - goto out; - } /* * Next, align both the file and mem bss up to the page size, * since this is where elf_bss was just zeroed up to, and where -- 2.34.1
