Date: Tue, 31 Oct 2023 02:40:54 +0200 From: Konstantin Belousov <kib@freebsd.org> To: Benjamin Kaduk <bjkfbsd@gmail.com> Cc: "Stephen J. Kiernan" <stevek@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 95335dd3c19e - main - rtld: introduce STATIC_TLS_EXTRA Message-ID: <ZUBNFvivvyU-guqh@kib.kiev.ua> In-Reply-To: <CAJ5_RoCx1zbpU4U1ZE2N%2BQCM6oVA4wwrM=dyP9%2Bqe2FqvHpv4w@mail.gmail.com> References: <202310301742.39UHgSPp011580@gitrepo.freebsd.org> <CAJ5_RoCx1zbpU4U1ZE2N%2BQCM6oVA4wwrM=dyP9%2Bqe2FqvHpv4w@mail.gmail.com>
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On Mon, Oct 30, 2023 at 10:56:52AM -0700, Benjamin Kaduk wrote: > On Mon, Oct 30, 2023 at 10:42 AM Stephen J. Kiernan <stevek@freebsd.org> > wrote: > > > The branch main has been updated by stevek: > > > > URL: > > https://cgit.FreeBSD.org/src/commit/?id=95335dd3c19e0ade161bb4dc8462fc3d045ce4f8 > > > > commit 95335dd3c19e0ade161bb4dc8462fc3d045ce4f8 > > Author: Stephen J. Kiernan <stevek@FreeBSD.org> > > AuthorDate: 2023-10-29 21:13:10 +0000 > > Commit: Stephen J. Kiernan <stevek@FreeBSD.org> > > CommitDate: 2023-10-30 17:42:05 +0000 > > > > rtld: introduce STATIC_TLS_EXTRA > > > > The new STATIC_TLS_EXTRA variable provides a means for applications > > to increases the size of the extra static TLS space allocated by > > rtld beyond the default of '128'. This extra static TLS space is used > > for objects loaded with dlopen. > > > > The value specified in the variable must be no less than the default > > value and no greater than the maximum allowed value for size_t type. > > > > > > I think that we want to have a maximum allowed value that is smaller than > SIZE_T_MAX, both to prevent chance of this being used in attacks and to > prevent integer overflow. > > Perhaps something large but not incredibly large, like 1M? What attacks? > > > > If an invalid value is specified, rtld will ignore it and just use > > the default value. > > > > The rtld(1) man page is updated to document this new option. > > > > Obtained from: Juniper Networks, Inc. > > Differential Revision: https://reviews.freebsd.org/D42025 > > --- > > libexec/rtld-elf/aarch64/reloc.c | 2 +- > > libexec/rtld-elf/amd64/reloc.c | 2 +- > > libexec/rtld-elf/arm/reloc.c | 3 ++- > > libexec/rtld-elf/i386/reloc.c | 2 +- > > libexec/rtld-elf/powerpc/reloc.c | 3 ++- > > libexec/rtld-elf/powerpc64/reloc.c | 3 ++- > > libexec/rtld-elf/riscv/reloc.c | 2 +- > > libexec/rtld-elf/rtld.1 | 8 +++++++- > > libexec/rtld-elf/rtld.c | 21 +++++++++++++++++---- > > libexec/rtld-elf/rtld.h | 1 + > > 10 files changed, 35 insertions(+), 12 deletions(-) > > > > diff --git a/libexec/rtld-elf/aarch64/reloc.c > > b/libexec/rtld-elf/aarch64/reloc.c > > index c8f09d797215..907377f2619a 100644 > > --- a/libexec/rtld-elf/aarch64/reloc.c > > +++ b/libexec/rtld-elf/aarch64/reloc.c > > @@ -521,7 +521,7 @@ allocate_initial_tls(Obj_Entry *objs) > > * use. > > */ > > tls_static_space = tls_last_offset + tls_last_size + > > - RTLD_STATIC_TLS_EXTRA; > > + ld_static_tls_extra; > > > > _tcb_set(allocate_tls(objs, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN)); > > } > > diff --git a/libexec/rtld-elf/amd64/reloc.c > > b/libexec/rtld-elf/amd64/reloc.c > > index ce74c54cc5c3..9c5887def356 100644 > > --- a/libexec/rtld-elf/amd64/reloc.c > > +++ b/libexec/rtld-elf/amd64/reloc.c > > @@ -527,7 +527,7 @@ allocate_initial_tls(Obj_Entry *objs) > > * offset allocated so far and adding a bit for dynamic > > * modules to use. > > */ > > - tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; > > + tls_static_space = tls_last_offset + ld_static_tls_extra; > > > > > This calculation could overflow, as I see it (likewise for the other archs). So do not do it.
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