* [PATCH] inotify: Use strscpy() for event->name copies
@ 2024-12-16 22:45 Kees Cook
2024-12-17 4:12 ` Matthew Wilcox
2024-12-18 10:35 ` Jan Kara
0 siblings, 2 replies; 4+ messages in thread
From: Kees Cook @ 2024-12-16 22:45 UTC (permalink / raw)
To: Jan Kara
Cc: Kees Cook, Amir Goldstein, linux-fsdevel, linux-kernel,
linux-hardening
Since we have already allocated "len + 1" space for event->name, make sure
that name->name cannot ever accidentally cause a copy overflow by calling
strscpy() instead of the unbounded strcpy() routine. This assists in
the ongoing efforts to remove the unsafe strcpy() API[1] from the kernel.
Link: https://github.com/KSPP/linux/issues/88 [1]
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Jan Kara <jack@suse.cz>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: linux-fsdevel@vger.kernel.org
---
fs/notify/inotify/inotify_fsnotify.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index 993375f0db67..cd7d11b0eb08 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -121,7 +121,7 @@ int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
event->sync_cookie = cookie;
event->name_len = len;
if (len)
- strcpy(event->name, name->name);
+ strscpy(event->name, name->name, event->name_len + 1);
ret = fsnotify_add_event(group, fsn_event, inotify_merge);
if (ret) {
--
2.34.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] inotify: Use strscpy() for event->name copies
2024-12-16 22:45 [PATCH] inotify: Use strscpy() for event->name copies Kees Cook
@ 2024-12-17 4:12 ` Matthew Wilcox
2024-12-17 7:51 ` Kees Cook
2024-12-18 10:35 ` Jan Kara
1 sibling, 1 reply; 4+ messages in thread
From: Matthew Wilcox @ 2024-12-17 4:12 UTC (permalink / raw)
To: Kees Cook
Cc: Jan Kara, Amir Goldstein, linux-fsdevel, linux-kernel,
linux-hardening
On Mon, Dec 16, 2024 at 02:45:15PM -0800, Kees Cook wrote:
> Since we have already allocated "len + 1" space for event->name, make sure
> that name->name cannot ever accidentally cause a copy overflow by calling
> strscpy() instead of the unbounded strcpy() routine. This assists in
> the ongoing efforts to remove the unsafe strcpy() API[1] from the kernel.
Since a qstr can't contain a NUL before the length, why not just use
memcpy()?
> event->name_len = len;
> if (len)
> - strcpy(event->name, name->name);
> + strscpy(event->name, name->name, event->name_len + 1);
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] inotify: Use strscpy() for event->name copies
2024-12-17 4:12 ` Matthew Wilcox
@ 2024-12-17 7:51 ` Kees Cook
0 siblings, 0 replies; 4+ messages in thread
From: Kees Cook @ 2024-12-17 7:51 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Jan Kara, Amir Goldstein, linux-fsdevel, linux-kernel,
linux-hardening
On December 16, 2024 8:12:07 PM PST, Matthew Wilcox <willy@infradead.org> wrote:
>On Mon, Dec 16, 2024 at 02:45:15PM -0800, Kees Cook wrote:
>> Since we have already allocated "len + 1" space for event->name, make sure
>> that name->name cannot ever accidentally cause a copy overflow by calling
>> strscpy() instead of the unbounded strcpy() routine. This assists in
>> the ongoing efforts to remove the unsafe strcpy() API[1] from the kernel.
>
>Since a qstr can't contain a NUL before the length, why not just use
>memcpy()?
>
>> event->name_len = len;
>> if (len)
>> - strcpy(event->name, name->name);
>> + strscpy(event->name, name->name, event->name_len + 1);
So that the destination is guaranteed to be NUL terminated no matter what's in the source. :) (i.e. try to limit unlikely conditions from expanding.)
--
Kees Cook
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] inotify: Use strscpy() for event->name copies
2024-12-16 22:45 [PATCH] inotify: Use strscpy() for event->name copies Kees Cook
2024-12-17 4:12 ` Matthew Wilcox
@ 2024-12-18 10:35 ` Jan Kara
1 sibling, 0 replies; 4+ messages in thread
From: Jan Kara @ 2024-12-18 10:35 UTC (permalink / raw)
To: Kees Cook
Cc: Jan Kara, Amir Goldstein, linux-fsdevel, linux-kernel,
linux-hardening
On Mon 16-12-24 14:45:15, Kees Cook wrote:
> Since we have already allocated "len + 1" space for event->name, make sure
> that name->name cannot ever accidentally cause a copy overflow by calling
> strscpy() instead of the unbounded strcpy() routine. This assists in
> the ongoing efforts to remove the unsafe strcpy() API[1] from the kernel.
>
> Link: https://github.com/KSPP/linux/issues/88 [1]
> Signed-off-by: Kees Cook <kees@kernel.org>
Thanks. Added to my tree.
Honza
> ---
> Cc: Jan Kara <jack@suse.cz>
> Cc: Amir Goldstein <amir73il@gmail.com>
> Cc: linux-fsdevel@vger.kernel.org
> ---
> fs/notify/inotify/inotify_fsnotify.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
> index 993375f0db67..cd7d11b0eb08 100644
> --- a/fs/notify/inotify/inotify_fsnotify.c
> +++ b/fs/notify/inotify/inotify_fsnotify.c
> @@ -121,7 +121,7 @@ int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
> event->sync_cookie = cookie;
> event->name_len = len;
> if (len)
> - strcpy(event->name, name->name);
> + strscpy(event->name, name->name, event->name_len + 1);
>
> ret = fsnotify_add_event(group, fsn_event, inotify_merge);
> if (ret) {
> --
> 2.34.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-12-16 22:45 [PATCH] inotify: Use strscpy() for event->name copies Kees Cook
2024-12-17 4:12 ` Matthew Wilcox
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2024-12-18 10:35 ` Jan Kara
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