On Mon, Aug 16, 2021 at 09:48:34PM +0200, David Hildenbrand wrote: > uselib() is the legacy systemcall for loading shared libraries. > Nowadays, applications use dlopen() to load shared libraries, completely > implemented in user space via mmap(). > > For example, glibc uses MAP_COPY to mmap shared libraries. While this > maps to MAP_PRIVATE | MAP_DENYWRITE on Linux, Linux ignores any > MAP_DENYWRITE specification from user space in mmap. > > With this change, all remaining in-tree users of MAP_DENYWRITE use it > to map an executable. We will be able to open shared libraries loaded > via uselib() writable, just as we already can via dlopen() from user > space. > > This is one step into the direction of removing MAP_DENYWRITE from the > kernel. This can be considered a minor user space visible change. > > Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > --- > arch/x86/ia32/ia32_aout.c | 2 +- > fs/binfmt_aout.c | 2 +- > fs/binfmt_elf.c | 2 +- > 3 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c > index 5e5b9fc2747f..321d7b22ad2d 100644 > --- a/arch/x86/ia32/ia32_aout.c > +++ b/arch/x86/ia32/ia32_aout.c > @@ -293,7 +293,7 @@ static int load_aout_library(struct file *file) > /* Now use mmap to map the library into memory. */ > error = vm_mmap(file, start_addr, ex.a_text + ex.a_data, > PROT_READ | PROT_WRITE | PROT_EXEC, > - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_32BIT, > + MAP_FIXED | MAP_PRIVATE | MAP_32BIT, > N_TXTOFF(ex)); > retval = error; > if (error != start_addr) > diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c > index 145917f734fe..d29de971d3f3 100644 > --- a/fs/binfmt_aout.c > +++ b/fs/binfmt_aout.c > @@ -309,7 +309,7 @@ static int load_aout_library(struct file *file) > /* Now use mmap to map the library into memory. */ > error = vm_mmap(file, start_addr, ex.a_text + ex.a_data, > PROT_READ | PROT_WRITE | PROT_EXEC, > - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE, > + MAP_FIXED | MAP_PRIVATE; > N_TXTOFF(ex)); Guess someone didn't care compile testing their code. This is now in mainline. Guenter
