diff mbox series

[5.16,v2] binfmt_elf: Avoid total_mapping_size for ET_EXEC

Message ID 20220228205518.1265798-1-keescook@chromium.org (mailing list archive)
State New, archived
Headers show
Series [5.16,v2] binfmt_elf: Avoid total_mapping_size for ET_EXEC | expand

Commit Message

Kees Cook Feb. 28, 2022, 8:55 p.m. UTC
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>
---
Here's the v5.16 backport.
---
 fs/binfmt_elf.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

Comments

matoro Feb. 28, 2022, 10:14 p.m. UTC | #1
On 2022-02-28 15:55, 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>
> ---
> Here's the v5.16 backport.
> ---
>  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 f8c7f26f1fbb..911a9e7044f4 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1135,14 +1135,25 @@ 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 load_addr_set is set to true later once the
> -		 * initial mapping is performed.)
> -		 */
> -		if (!load_addr_set) {
> +			/*
> +			 * 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 the trick!  Thank you so much!!
Kees Cook Feb. 28, 2022, 10:53 p.m. UTC | #2
On Mon, Feb 28, 2022 at 05:14:26PM -0500, matoro wrote:
> On 2022-02-28 15:55, 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>
> > ---
> > Here's the v5.16 backport.
> > ---
> >  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 f8c7f26f1fbb..911a9e7044f4 100644
> > --- a/fs/binfmt_elf.c
> > +++ b/fs/binfmt_elf.c
> > @@ -1135,14 +1135,25 @@ 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 load_addr_set is set to true later once the
> > -		 * initial mapping is performed.)
> > -		 */
> > -		if (!load_addr_set) {
> > +			/*
> > +			 * 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 the trick!  Thank you so much!!

Excellent; thank you for testing! I'll send this to Linus shortly.
John Paul Adrian Glaubitz March 1, 2022, 12:36 p.m. UTC | #3
Hello!

On 2/28/22 21:55, 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>
> ---
> Here's the v5.16 backport.
> ---
>  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 f8c7f26f1fbb..911a9e7044f4 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1135,14 +1135,25 @@ 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 load_addr_set is set to true later once the
> -		 * initial mapping is performed.)
> -		 */
> -		if (!load_addr_set) {
> +			/*
> +			 * 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) {

I can confirm that this patch fixes the issue for me.

Tested-By: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>

Thanks,
Adrian
diff mbox series

Patch

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index f8c7f26f1fbb..911a9e7044f4 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1135,14 +1135,25 @@  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 load_addr_set is set to true later once the
-		 * initial mapping is performed.)
-		 */
-		if (!load_addr_set) {
+			/*
+			 * 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) {