strncpy() is in the process of being replaced as it is deprecated [1].
We should move towards safer and less ambiguous string interfaces.
Looking at vmcoredd_header's definition:
| struct vmcoredd_header {
| __u32 n_namesz; /* Name size */
| __u32 n_descsz; /* Content size */
| __u32 n_type; /* NT_VMCOREDD */
| __u8 name[8]; /* LINUX\0\0\0 */
| __u8 dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Device dump's name */
| };
.. we see that @name wants to be NUL-padded.
We're copying data->dump_name which is defined as:
| char dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Unique name of the dump */
.. which shares the same size as vdd_hdr->dump_name. Let's make sure we
NUL-pad this as well.
Use strscpy_pad() which NUL-terminates and NUL-pads its destination
buffers. Specifically, use the new 2-argument version of strscpy_pad
introduced in Commit e6584c3964f2f ("string: Allow 2-argument
strscpy()").
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Changes in v2:
- don't mark buffers as __nonstring, instead use a string API (thanks Kees)
- Link to v1: https://lore.kernel.org/r/[email protected]
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
fs/proc/vmcore.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 1fb213f379a5..5d08d4d159d3 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -1370,9 +1370,8 @@ static void vmcoredd_write_header(void *buf, struct vmcoredd_data *data,
vdd_hdr->n_descsz = size + sizeof(vdd_hdr->dump_name);
vdd_hdr->n_type = NT_VMCOREDD;
- strncpy((char *)vdd_hdr->name, VMCOREDD_NOTE_NAME,
- sizeof(vdd_hdr->name));
- memcpy(vdd_hdr->dump_name, data->dump_name, sizeof(vdd_hdr->dump_name));
+ strscpy_pad(vdd_hdr->name, VMCOREDD_NOTE_NAME);
+ strscpy_pad(vdd_hdr->dump_name, data->dump_name);
}
/**
---
base-commit: 928a87efa42302a23bb9554be081a28058495f22
change-id: 20240327-strncpy-fs-proc-vmcore-c-b18d761feaef
Best regards,
--
Justin Stitt <[email protected]>
On 04/01/24 at 06:39pm, Justin Stitt wrote:
> strncpy() is in the process of being replaced as it is deprecated [1].
> We should move towards safer and less ambiguous string interfaces.
>
> Looking at vmcoredd_header's definition:
> | struct vmcoredd_header {
> | __u32 n_namesz; /* Name size */
> | __u32 n_descsz; /* Content size */
> | __u32 n_type; /* NT_VMCOREDD */
> | __u8 name[8]; /* LINUX\0\0\0 */
> | __u8 dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Device dump's name */
> | };
> ... we see that @name wants to be NUL-padded.
>
> We're copying data->dump_name which is defined as:
> | char dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Unique name of the dump */
> ... which shares the same size as vdd_hdr->dump_name. Let's make sure we
> NUL-pad this as well.
>
> Use strscpy_pad() which NUL-terminates and NUL-pads its destination
> buffers. Specifically, use the new 2-argument version of strscpy_pad
> introduced in Commit e6584c3964f2f ("string: Allow 2-argument
> strscpy()").
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> Changes in v2:
> - don't mark buffers as __nonstring, instead use a string API (thanks Kees)
> - Link to v1: https://lore.kernel.org/r/[email protected]
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> fs/proc/vmcore.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 1fb213f379a5..5d08d4d159d3 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -1370,9 +1370,8 @@ static void vmcoredd_write_header(void *buf, struct vmcoredd_data *data,
> vdd_hdr->n_descsz = size + sizeof(vdd_hdr->dump_name);
> vdd_hdr->n_type = NT_VMCOREDD;
>
> - strncpy((char *)vdd_hdr->name, VMCOREDD_NOTE_NAME,
> - sizeof(vdd_hdr->name));
> - memcpy(vdd_hdr->dump_name, data->dump_name, sizeof(vdd_hdr->dump_name));
> + strscpy_pad(vdd_hdr->name, VMCOREDD_NOTE_NAME);
> + strscpy_pad(vdd_hdr->dump_name, data->dump_name);
LGTM, thx
Acked-by: Baoquan He <[email protected]>
On Mon, Apr 01, 2024 at 06:39:55PM +0000, Justin Stitt wrote:
> strncpy() is in the process of being replaced as it is deprecated [1].
> We should move towards safer and less ambiguous string interfaces.
>
> Looking at vmcoredd_header's definition:
> | struct vmcoredd_header {
> | __u32 n_namesz; /* Name size */
> | __u32 n_descsz; /* Content size */
> | __u32 n_type; /* NT_VMCOREDD */
> | __u8 name[8]; /* LINUX\0\0\0 */
> | __u8 dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Device dump's name */
> | };
> ... we see that @name wants to be NUL-padded.
>
> We're copying data->dump_name which is defined as:
> | char dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Unique name of the dump */
> ... which shares the same size as vdd_hdr->dump_name. Let's make sure we
> NUL-pad this as well.
>
> Use strscpy_pad() which NUL-terminates and NUL-pads its destination
> buffers. Specifically, use the new 2-argument version of strscpy_pad
> introduced in Commit e6584c3964f2f ("string: Allow 2-argument
> strscpy()").
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Looks good; thanks!
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook