| Message ID | 20220228194613.1149432-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | binfmt_elf: Avoid total_mapping_size for ET_EXEC | expand |
On 2022-02-28 14:46, Kees Cook wrote: > Partially revert commit 5f501d555653 ("binfmt_elf: reintroduce using > MAP_FIXED_NOREPLACE"). > > At least ia64 has ET_EXEC PT_LOAD segments that are not virtual-address > contiguous (but _are_ file-offset contiguous). This would result in > giant mapping attempts to cover the entire span, including the virtual > address range hole. Disable total_mapping_size for ET_EXEC, which > reduces the MAP_FIXED_NOREPLACE coverage to only the first PT_LOAD: > > $ readelf -lW /usr/bin/gcc > ... > Program Headers: > Type Offset VirtAddr PhysAddr FileSiz MemSiz > ... > ... > LOAD 0x000000 0x4000000000000000 0x4000000000000000 0x00b5a0 0x00b5a0 > ... > LOAD 0x00b5a0 0x600000000000b5a0 0x600000000000b5a0 0x0005ac 0x000710 > ... > ... > ^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^^^^^^^ ^^^^^^^^ > > File offset range : 0x000000-0x00bb4c > 0x00bb4c bytes > > Virtual address range : 0x4000000000000000-0x600000000000bcb0 > 0x200000000000bcb0 bytes > > Ironically, this is the reverse of the problem that originally caused > problems with ET_EXEC and MAP_FIXED_NOREPLACE: overlaps. This problem > is > with holes. Future work could restore full coverage if > load_elf_binary() > were to perform mappings in a separate phase from the loading (where > it could resolve both overlaps and holes). > > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: Eric Biederman <ebiederm@xmission.com> > Cc: linux-fsdevel@vger.kernel.org > Cc: linux-mm@kvack.org > Reported-by: matoro <matoro_mailinglist_kernel@matoro.tk> > Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> > Fixes: 5f501d555653 ("binfmt_elf: reintroduce using > MAP_FIXED_NOREPLACE") > Link: > https://lore.kernel.org/r/a3edd529-c42d-3b09-135c-7e98a15b150f@leemhuis.info > Cc: stable@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > matoro (or anyone else) can you please test this? > --- > fs/binfmt_elf.c | 25 ++++++++++++++++++------- > 1 file changed, 18 insertions(+), 7 deletions(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 9bea703ed1c2..474b44032c65 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -1136,14 +1136,25 @@ static int load_elf_binary(struct linux_binprm > *bprm) > * is then page aligned. > */ > load_bias = ELF_PAGESTART(load_bias - vaddr); > - } > > - /* > - * Calculate the entire size of the ELF mapping (total_size). > - * (Note that first_pt_load is set to false later once the > - * initial mapping is performed.) > - */ > - if (first_pt_load) { > + /* > + * Calculate the entire size of the ELF mapping > + * (total_size), used for the initial mapping, > + * due to first_pt_load which is set to false later > + * once the initial mapping is performed. > + * > + * Note that this is only sensible when the LOAD > + * segments are contiguous (or overlapping). If > + * used for LOADs that are far apart, this would > + * cause the holes between LOADs to be mapped, > + * running the risk of having the mapping fail, > + * as it would be larger than the ELF file itself. > + * > + * As a result, only ET_DYN does this, since > + * some ET_EXEC (e.g. ia64) may have virtual > + * memory holes between LOADs. > + * > + */ > total_size = total_mapping_size(elf_phdata, > elf_ex->e_phnum); > if (!total_size) { This does not apply for me, I'm looking around and can't find any reference to the first_pt_load variable you're removing there? What commit/tag are you applying this on top of?
On Mon, Feb 28, 2022 at 03:31:00PM -0500, matoro wrote: > On 2022-02-28 14:46, Kees Cook wrote: > > Partially revert commit 5f501d555653 ("binfmt_elf: reintroduce using > > MAP_FIXED_NOREPLACE"). > > > > At least ia64 has ET_EXEC PT_LOAD segments that are not virtual-address > > contiguous (but _are_ file-offset contiguous). This would result in > > giant mapping attempts to cover the entire span, including the virtual > > address range hole. Disable total_mapping_size for ET_EXEC, which > > reduces the MAP_FIXED_NOREPLACE coverage to only the first PT_LOAD: > > > > $ readelf -lW /usr/bin/gcc > > ... > > Program Headers: > > Type Offset VirtAddr PhysAddr FileSiz MemSiz > > ... > > ... > > LOAD 0x000000 0x4000000000000000 0x4000000000000000 0x00b5a0 0x00b5a0 > > ... > > LOAD 0x00b5a0 0x600000000000b5a0 0x600000000000b5a0 0x0005ac 0x000710 > > ... > > ... > > ^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^^^^^^^ ^^^^^^^^ > > > > File offset range : 0x000000-0x00bb4c > > 0x00bb4c bytes > > > > Virtual address range : 0x4000000000000000-0x600000000000bcb0 > > 0x200000000000bcb0 bytes > > > > Ironically, this is the reverse of the problem that originally caused > > problems with ET_EXEC and MAP_FIXED_NOREPLACE: overlaps. This problem is > > with holes. Future work could restore full coverage if load_elf_binary() > > were to perform mappings in a separate phase from the loading (where > > it could resolve both overlaps and holes). > > > > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > > Cc: Eric Biederman <ebiederm@xmission.com> > > Cc: linux-fsdevel@vger.kernel.org > > Cc: linux-mm@kvack.org > > Reported-by: matoro <matoro_mailinglist_kernel@matoro.tk> > > Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> > > Fixes: 5f501d555653 ("binfmt_elf: reintroduce using > > MAP_FIXED_NOREPLACE") > > Link: > > https://lore.kernel.org/r/a3edd529-c42d-3b09-135c-7e98a15b150f@leemhuis.info > > Cc: stable@vger.kernel.org > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > matoro (or anyone else) can you please test this? > > --- > > fs/binfmt_elf.c | 25 ++++++++++++++++++------- > > 1 file changed, 18 insertions(+), 7 deletions(-) > > > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > > index 9bea703ed1c2..474b44032c65 100644 > > --- a/fs/binfmt_elf.c > > +++ b/fs/binfmt_elf.c > > @@ -1136,14 +1136,25 @@ static int load_elf_binary(struct linux_binprm > > *bprm) > > * is then page aligned. > > */ > > load_bias = ELF_PAGESTART(load_bias - vaddr); > > - } > > > > - /* > > - * Calculate the entire size of the ELF mapping (total_size). > > - * (Note that first_pt_load is set to false later once the > > - * initial mapping is performed.) > > - */ > > - if (first_pt_load) { > > + /* > > + * Calculate the entire size of the ELF mapping > > + * (total_size), used for the initial mapping, > > + * due to first_pt_load which is set to false later > > + * once the initial mapping is performed. > > + * > > + * Note that this is only sensible when the LOAD > > + * segments are contiguous (or overlapping). If > > + * used for LOADs that are far apart, this would > > + * cause the holes between LOADs to be mapped, > > + * running the risk of having the mapping fail, > > + * as it would be larger than the ELF file itself. > > + * > > + * As a result, only ET_DYN does this, since > > + * some ET_EXEC (e.g. ia64) may have virtual > > + * memory holes between LOADs. > > + * > > + */ > > total_size = total_mapping_size(elf_phdata, > > elf_ex->e_phnum); > > if (!total_size) { > > This does not apply for me, I'm looking around and can't find any reference > to the first_pt_load variable you're removing there? What commit/tag are > you applying this on top of? Ah, yeah, this is against linux-next. Let me send a backport, one sec...
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 9bea703ed1c2..474b44032c65 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1136,14 +1136,25 @@ static int load_elf_binary(struct linux_binprm *bprm) * is then page aligned. */ load_bias = ELF_PAGESTART(load_bias - vaddr); - } - /* - * Calculate the entire size of the ELF mapping (total_size). - * (Note that first_pt_load is set to false later once the - * initial mapping is performed.) - */ - if (first_pt_load) { + /* + * Calculate the entire size of the ELF mapping + * (total_size), used for the initial mapping, + * due to first_pt_load which is set to false later + * once the initial mapping is performed. + * + * Note that this is only sensible when the LOAD + * segments are contiguous (or overlapping). If + * used for LOADs that are far apart, this would + * cause the holes between LOADs to be mapped, + * running the risk of having the mapping fail, + * as it would be larger than the ELF file itself. + * + * As a result, only ET_DYN does this, since + * some ET_EXEC (e.g. ia64) may have virtual + * memory holes between LOADs. + * + */ total_size = total_mapping_size(elf_phdata, elf_ex->e_phnum); if (!total_size) {
Partially revert commit 5f501d555653 ("binfmt_elf: reintroduce using MAP_FIXED_NOREPLACE"). At least ia64 has ET_EXEC PT_LOAD segments that are not virtual-address contiguous (but _are_ file-offset contiguous). This would result in giant mapping attempts to cover the entire span, including the virtual address range hole. Disable total_mapping_size for ET_EXEC, which reduces the MAP_FIXED_NOREPLACE coverage to only the first PT_LOAD: $ readelf -lW /usr/bin/gcc ... Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz ... ... LOAD 0x000000 0x4000000000000000 0x4000000000000000 0x00b5a0 0x00b5a0 ... LOAD 0x00b5a0 0x600000000000b5a0 0x600000000000b5a0 0x0005ac 0x000710 ... ... ^^^^^^^^ ^^^^^^^^^^^^^^^^^^ ^^^^^^^^ ^^^^^^^^ File offset range : 0x000000-0x00bb4c 0x00bb4c bytes Virtual address range : 0x4000000000000000-0x600000000000bcb0 0x200000000000bcb0 bytes Ironically, this is the reverse of the problem that originally caused problems with ET_EXEC and MAP_FIXED_NOREPLACE: overlaps. This problem is with holes. Future work could restore full coverage if load_elf_binary() were to perform mappings in a separate phase from the loading (where it could resolve both overlaps and holes). Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Eric Biederman <ebiederm@xmission.com> Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Reported-by: matoro <matoro_mailinglist_kernel@matoro.tk> Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Fixes: 5f501d555653 ("binfmt_elf: reintroduce using MAP_FIXED_NOREPLACE") Link: https://lore.kernel.org/r/a3edd529-c42d-3b09-135c-7e98a15b150f@leemhuis.info Cc: stable@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> --- matoro (or anyone else) can you please test this? --- fs/binfmt_elf.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-)