[PATCH stable 5.15] lib/buildid: Handle memfd_secret() files in build_id_parse()

[PATCH stable 5.15] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Chen Linxuan]

Backport of a similar change from commit 5ac9b4e935df ("lib/buildid:
Handle memfd_secret() files in build_id_parse()") to address an issue
where accessing secret memfd contents through build_id_parse() would
trigger faults.

Original report and repro can be found in [0].

  [0] https://lore.kernel.org/bpf/ZwyG8Uro%2FSyTXAni@ly-workstation/

This repro will cause BUG: unable to handle kernel paging request in
build_id_parse in 5.15/6.1/6.6.

Some other discussions can be found in [1].

  [1] https://lore.kernel.org/bpf/20241104175256.2327164-1-jolsa@kernel.org/T/#u

Cc: stable@vger.kernel.org
Fixes: 88a16a130933 ("perf: Add build id data in mmap2 event")
Signed-off-by: Chen Linxuan <chenlinxuan@deepin.org>
---
 lib/buildid.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/buildid.c b/lib/buildid.c
index 9fc46366597e..9db35305f257 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -5,6 +5,7 @@
 #include <linux/elf.h>
 #include <linux/kernel.h>
 #include <linux/pagemap.h>
+#include <linux/secretmem.h>
 
 #define BUILD_ID 3
 
@@ -157,6 +158,12 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
 	if (!vma->vm_file)
 		return -EINVAL;
 
+#ifdef CONFIG_SECRETMEM
+	/* reject secretmem folios created with memfd_secret() */
+	if (vma->vm_file->f_mapping->a_ops == &secretmem_aops)
+		return -EFAULT;
+#endif
+
 	page = find_get_page(vma->vm_file->f_mapping, 0);
 	if (!page)
 		return -EFAULT;	/* page not mapped */
-- 
2.48.1

Re: [PATCH stable 5.15] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
⚠️ Found matching upstream commit but patch is missing proper reference to it

Found matching upstream commit: 5ac9b4e935dfc6af41eee2ddc21deb5c36507a9f

WARNING: Author mismatch between patch and found commit:
Backport author: Chen Linxuan<chenlinxuan@deepin.org>
Commit author: Andrii Nakryiko<andrii@kernel.org>

Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Not found
6.1.y | Not found

Note: The patch differs from the upstream commit:
---
1:  5ac9b4e935dfc ! 1:  31a498155ca94 lib/buildid: Handle memfd_secret() files in build_id_parse()
    @@
      ## Metadata ##
    -Author: Andrii Nakryiko <andrii@kernel.org>
    +Author: Chen Linxuan <chenlinxuan@deepin.org>
     
      ## Commit message ##
         lib/buildid: Handle memfd_secret() files in build_id_parse()
     
    -    >From memfd_secret(2) manpage:
    +    Backport of a similar change from commit 5ac9b4e935df ("lib/buildid:
    +    Handle memfd_secret() files in build_id_parse()") to address an issue
    +    where accessing secret memfd contents through build_id_parse() would
    +    trigger faults.
     
    -      The memory areas backing the file created with memfd_secret(2) are
    -      visible only to the processes that have access to the file descriptor.
    -      The memory region is removed from the kernel page tables and only the
    -      page tables of the processes holding the file descriptor map the
    -      corresponding physical memory. (Thus, the pages in the region can't be
    -      accessed by the kernel itself, so that, for example, pointers to the
    -      region can't be passed to system calls.)
    -
    -    We need to handle this special case gracefully in build ID fetching
    -    code. Return -EFAULT whenever secretmem file is passed to build_id_parse()
    -    family of APIs. Original report and repro can be found in [0].
    +    Original report and repro can be found in [0].
     
           [0] https://lore.kernel.org/bpf/ZwyG8Uro%2FSyTXAni@ly-workstation/
     
    -    Fixes: de3ec364c3c3 ("lib/buildid: add single folio-based file reader abstraction")
    -    Reported-by: Yi Lai <yi1.lai@intel.com>
    -    Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
    -    Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
    -    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    -    Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
    -    Link: https://lore.kernel.org/bpf/20241017175431.6183-A-hca@linux.ibm.com
    -    Link: https://lore.kernel.org/bpf/20241017174713.2157873-1-andrii@kernel.org
    +    This repro will cause BUG: unable to handle kernel paging request in
    +    build_id_parse in 5.15/6.1/6.6.
    +
    +    Some other discussions can be found in [1].
    +
    +      [1] https://lore.kernel.org/bpf/20241104175256.2327164-1-jolsa@kernel.org/T/#u
    +
    +    Cc: stable@vger.kernel.org
    +    Fixes: 88a16a130933 ("perf: Add build id data in mmap2 event")
    +    Signed-off-by: Chen Linxuan <chenlinxuan@deepin.org>
     
      ## lib/buildid.c ##
     @@
    @@ lib/buildid.c
      
      #define BUILD_ID 3
      
    -@@ lib/buildid.c: static int freader_get_folio(struct freader *r, loff_t file_off)
    - 
    - 	freader_put_folio(r);
    +@@ lib/buildid.c: int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
    + 	if (!vma->vm_file)
    + 		return -EINVAL;
      
    ++#ifdef CONFIG_SECRETMEM
     +	/* reject secretmem folios created with memfd_secret() */
    -+	if (secretmem_mapping(r->file->f_mapping))
    ++	if (vma->vm_file->f_mapping->a_ops == &secretmem_aops)
     +		return -EFAULT;
    ++#endif
     +
    - 	r->folio = filemap_get_folio(r->file->f_mapping, file_off >> PAGE_SHIFT);
    - 
    - 	/* if sleeping is allowed, wait for the page, if necessary */
    + 	page = find_get_page(vma->vm_file->f_mapping, 0);
    + 	if (!page)
    + 		return -EFAULT;	/* page not mapped */
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |

[PATCH stable 5.15] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Chen Linxuan]

[ Upstream commit 5ac9b4e935dfc6af41eee2ddc21deb5c36507a9f ]

>From memfd_secret(2) manpage:

  The memory areas backing the file created with memfd_secret(2) are
  visible only to the processes that have access to the file descriptor.
  The memory region is removed from the kernel page tables and only the
  page tables of the processes holding the file descriptor map the
  corresponding physical memory. (Thus, the pages in the region can't be
  accessed by the kernel itself, so that, for example, pointers to the
  region can't be passed to system calls.)

We need to handle this special case gracefully in build ID fetching
code. Return -EFAULT whenever secretmem file is passed to build_id_parse()
family of APIs. Original report and repro can be found in [0].

  [0] https://lore.kernel.org/bpf/ZwyG8Uro%2FSyTXAni@ly-workstation/

Fixes: de3ec364c3c3 ("lib/buildid: add single folio-based file reader abstraction")
Reported-by: Yi Lai <yi1.lai@intel.com>
Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Link: https://lore.kernel.org/bpf/20241017175431.6183-A-hca@linux.ibm.com
Link: https://lore.kernel.org/bpf/20241017174713.2157873-1-andrii@kernel.org
[ Linxuan: perform an equivalent direct check without folio-based changes ]
Cc: stable@vger.kernel.org
Fixes: 88a16a130933 ("perf: Add build id data in mmap2 event")
Signed-off-by: Chen Linxuan <chenlinxuan@deepin.org>
---

Some previous discussions can be found in the following links:
https://lore.kernel.org/stable/05D0A9F7DE394601+20250311100555.310788-2-chenlinxuan@deepin.org/

---
 lib/buildid.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/buildid.c b/lib/buildid.c
index 9fc46366597e..6249bd47fb0b 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -5,6 +5,7 @@
 #include <linux/elf.h>
 #include <linux/kernel.h>
 #include <linux/pagemap.h>
+#include <linux/secretmem.h>
 
 #define BUILD_ID 3
 
@@ -157,6 +158,12 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
 	if (!vma->vm_file)
 		return -EINVAL;
 
+#ifdef CONFIG_SECRETMEM
+       /* reject secretmem folios created with memfd_secret() */
+       if (vma->vm_file->f_mapping->a_ops == &secretmem_aops)
+               return -EFAULT;
+#endif
+
 	page = find_get_page(vma->vm_file->f_mapping, 0);
 	if (!page)
 		return -EFAULT;	/* page not mapped */
-- 
2.48.1

Re: [PATCH stable 5.15] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 5ac9b4e935dfc6af41eee2ddc21deb5c36507a9f

WARNING: Author mismatch between patch and upstream commit:
Backport author: Chen Linxuan<chenlinxuan@deepin.org>
Commit author: Andrii Nakryiko<andrii@kernel.org>

Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Not found
6.1.y | Not found

Note: The patch differs from the upstream commit:
---
1:  5ac9b4e935dfc < -:  ------------- lib/buildid: Handle memfd_secret() files in build_id_parse()
-:  ------------- > 1:  3c1e0975ba21f lib/buildid: Handle memfd_secret() files in build_id_parse()
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |