* Re: [PATCH] mm/madvise: process_madvise() drop capability check if same mm
2024-09-13 14:06 [PATCH] mm/madvise: process_madvise() drop capability check if same mm Lorenzo Stoakes
@ 2024-09-13 14:31 ` Liam R. Howlett
2024-09-13 14:35 ` Liam R. Howlett
2024-09-13 14:51 ` Vlastimil Babka
` (2 subsequent siblings)
3 siblings, 1 reply; 6+ messages in thread
From: Liam R. Howlett @ 2024-09-13 14:31 UTC (permalink / raw)
To: Lorenzo Stoakes
Cc: Andrew Morton, linux-mm, linux-kernel, Vlastimil Babka,
Shakeel Butt, Suren Baghdasaryan
* Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [240913 10:06]:
> In commit 96cfe2c0fd23 ("mm/madvise: replace ptrace attach requirement for
> process_madvise") process_madvise() was updated to require the caller to
> possess the CAP_SYS_NICE capability to perform the operation, in addition
> to a check against PTRACE_MODE_READ performed by mm_access().
>
> The mm_access() function explicitly checks to see if the address space of
> the process being referenced is the current one, in which case no check is
> performed.
>
> We, however, do not do this when checking the CAP_SYS_NICE capability. This
> means that we insist on the caller possessing this capability in order to
> perform madvise() operations on its own address space, which seems
> nonsensical.
>
> Simply add a check to allow for an invocation of this function with pidfd
> set to the current process without elevation.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Probably needs a fixes 96cfe2c0fd23 tag?
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> ---
> mm/madvise.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 4e64770be16c..ff139e57cca2 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1520,7 +1520,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> * Require CAP_SYS_NICE for influencing process performance. Note that
> * only non-destructive hints are currently supported.
> */
> - if (!capable(CAP_SYS_NICE)) {
> + if (mm != current->mm && !capable(CAP_SYS_NICE)) {
> ret = -EPERM;
> goto release_mm;
> }
> --
> 2.46.0
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/madvise: process_madvise() drop capability check if same mm
2024-09-13 14:31 ` Liam R. Howlett
@ 2024-09-13 14:35 ` Liam R. Howlett
0 siblings, 0 replies; 6+ messages in thread
From: Liam R. Howlett @ 2024-09-13 14:35 UTC (permalink / raw)
To: Shakeel Butt
Cc: Lorenzo Stoakes, Andrew Morton, linux-mm, linux-kernel,
Vlastimil Babka, Suren Baghdasaryan
..Add Shakeel's new email address
* Liam R. Howlett <Liam.Howlett@oracle.com> [240913 10:31]:
> * Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [240913 10:06]:
> > In commit 96cfe2c0fd23 ("mm/madvise: replace ptrace attach requirement for
> > process_madvise") process_madvise() was updated to require the caller to
> > possess the CAP_SYS_NICE capability to perform the operation, in addition
> > to a check against PTRACE_MODE_READ performed by mm_access().
> >
> > The mm_access() function explicitly checks to see if the address space of
> > the process being referenced is the current one, in which case no check is
> > performed.
> >
> > We, however, do not do this when checking the CAP_SYS_NICE capability. This
> > means that we insist on the caller possessing this capability in order to
> > perform madvise() operations on its own address space, which seems
> > nonsensical.
> >
> > Simply add a check to allow for an invocation of this function with pidfd
> > set to the current process without elevation.
> >
> > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
>
> Probably needs a fixes 96cfe2c0fd23 tag?
>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
>
> > ---
> > mm/madvise.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index 4e64770be16c..ff139e57cca2 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -1520,7 +1520,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> > * Require CAP_SYS_NICE for influencing process performance. Note that
> > * only non-destructive hints are currently supported.
> > */
> > - if (!capable(CAP_SYS_NICE)) {
> > + if (mm != current->mm && !capable(CAP_SYS_NICE)) {
> > ret = -EPERM;
> > goto release_mm;
> > }
> > --
> > 2.46.0
> >
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm/madvise: process_madvise() drop capability check if same mm
2024-09-13 14:06 [PATCH] mm/madvise: process_madvise() drop capability check if same mm Lorenzo Stoakes
2024-09-13 14:31 ` Liam R. Howlett
@ 2024-09-13 14:51 ` Vlastimil Babka
2024-09-13 15:56 ` Shakeel Butt
2024-09-15 7:50 ` David Rientjes
3 siblings, 0 replies; 6+ messages in thread
From: Vlastimil Babka @ 2024-09-13 14:51 UTC (permalink / raw)
To: Lorenzo Stoakes, Andrew Morton
Cc: linux-mm, linux-kernel, Liam Howlett, Shakeel Butt, Suren Baghdasaryan
On 9/13/24 16:06, Lorenzo Stoakes wrote:
> In commit 96cfe2c0fd23 ("mm/madvise: replace ptrace attach requirement for
> process_madvise") process_madvise() was updated to require the caller to
> possess the CAP_SYS_NICE capability to perform the operation, in addition
> to a check against PTRACE_MODE_READ performed by mm_access().
>
> The mm_access() function explicitly checks to see if the address space of
> the process being referenced is the current one, in which case no check is
> performed.
>
> We, however, do not do this when checking the CAP_SYS_NICE capability. This
> means that we insist on the caller possessing this capability in order to
> perform madvise() operations on its own address space, which seems
> nonsensical.
>
> Simply add a check to allow for an invocation of this function with pidfd
> set to the current process without elevation.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/madvise.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 4e64770be16c..ff139e57cca2 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1520,7 +1520,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> * Require CAP_SYS_NICE for influencing process performance. Note that
> * only non-destructive hints are currently supported.
> */
> - if (!capable(CAP_SYS_NICE)) {
> + if (mm != current->mm && !capable(CAP_SYS_NICE)) {
> ret = -EPERM;
> goto release_mm;
> }
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/madvise: process_madvise() drop capability check if same mm
2024-09-13 14:06 [PATCH] mm/madvise: process_madvise() drop capability check if same mm Lorenzo Stoakes
2024-09-13 14:31 ` Liam R. Howlett
2024-09-13 14:51 ` Vlastimil Babka
@ 2024-09-13 15:56 ` Shakeel Butt
2024-09-15 7:50 ` David Rientjes
3 siblings, 0 replies; 6+ messages in thread
From: Shakeel Butt @ 2024-09-13 15:56 UTC (permalink / raw)
To: Lorenzo Stoakes
Cc: Andrew Morton, linux-mm, linux-kernel, Vlastimil Babka,
Liam Howlett, Shakeel Butt, Suren Baghdasaryan
On Fri, Sep 13, 2024 at 03:06:28PM GMT, Lorenzo Stoakes wrote:
> In commit 96cfe2c0fd23 ("mm/madvise: replace ptrace attach requirement for
> process_madvise") process_madvise() was updated to require the caller to
> possess the CAP_SYS_NICE capability to perform the operation, in addition
> to a check against PTRACE_MODE_READ performed by mm_access().
>
> The mm_access() function explicitly checks to see if the address space of
> the process being referenced is the current one, in which case no check is
> performed.
>
> We, however, do not do this when checking the CAP_SYS_NICE capability. This
> means that we insist on the caller possessing this capability in order to
> perform madvise() operations on its own address space, which seems
> nonsensical.
>
> Simply add a check to allow for an invocation of this function with pidfd
> set to the current process without elevation.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/madvise: process_madvise() drop capability check if same mm
2024-09-13 14:06 [PATCH] mm/madvise: process_madvise() drop capability check if same mm Lorenzo Stoakes
` (2 preceding siblings ...)
2024-09-13 15:56 ` Shakeel Butt
@ 2024-09-15 7:50 ` David Rientjes
3 siblings, 0 replies; 6+ messages in thread
From: David Rientjes @ 2024-09-15 7:50 UTC (permalink / raw)
To: Lorenzo Stoakes
Cc: Andrew Morton, linux-mm, linux-kernel, Vlastimil Babka,
Liam Howlett, Shakeel Butt, Suren Baghdasaryan
On Fri, 13 Sep 2024, Lorenzo Stoakes wrote:
> In commit 96cfe2c0fd23 ("mm/madvise: replace ptrace attach requirement for
> process_madvise") process_madvise() was updated to require the caller to
> possess the CAP_SYS_NICE capability to perform the operation, in addition
> to a check against PTRACE_MODE_READ performed by mm_access().
>
> The mm_access() function explicitly checks to see if the address space of
> the process being referenced is the current one, in which case no check is
> performed.
>
> We, however, do not do this when checking the CAP_SYS_NICE capability. This
> means that we insist on the caller possessing this capability in order to
> perform madvise() operations on its own address space, which seems
> nonsensical.
>
> Simply add a check to allow for an invocation of this function with pidfd
> set to the current process without elevation.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Rientjes <rientjes@google.com>
^ permalink raw reply [flat|nested] 6+ messages in thread