On Tue, Sep 12, 2023 at 09:07:36AM +0800, Cong Liu wrote:
> when compiling with smatch check, the following errors were encountered:
>
> drivers/vfio/vfio_main.c:957 vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
>
> this patch fix these error.
>
> Signed-off-by: Cong Liu <[email protected]>
> ---
> drivers/vfio/vfio_main.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 40732e8ed4c6..68a0a5081161 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -938,12 +938,13 @@ static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
> void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> u32 req_nodes)
> {
> - struct interval_tree_node *prev, *curr, *comb_start, *comb_end;
> + struct interval_tree_node *prev, *curr;
> + struct interval_tree_node *comb_start = NULL, *comb_end = NULL;
> unsigned long min_gap, curr_gap;
>
> /* Special shortcut when a single range is required */
> if (req_nodes == 1) {
> - unsigned long last;
> + unsigned long last = 0;
>
> comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
> curr = comb_start;
These are not possible unless the list is empty, and assigning
zero/null isn't an improvement for that case it will just crash
Jason
when compiling with smatch check, the following errors were encountered:
drivers/vfio/vfio_main.c:957 vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
this patch fix these error.
Signed-off-by: Cong Liu <[email protected]>
---
drivers/vfio/vfio_main.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 40732e8ed4c6..96d2f3030ebb 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -938,14 +938,17 @@ static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
u32 req_nodes)
{
- struct interval_tree_node *prev, *curr, *comb_start, *comb_end;
+ struct interval_tree_node *prev, *curr;
+ struct interval_tree_node *comb_start = NULL, *comb_end = NULL;
unsigned long min_gap, curr_gap;
/* Special shortcut when a single range is required */
if (req_nodes == 1) {
- unsigned long last;
+ unsigned long last = 0;
comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
+ if (!comb_start)
+ return;
curr = comb_start;
while (curr) {
last = curr->last;
@@ -963,6 +966,10 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
prev = NULL;
min_gap = ULONG_MAX;
curr = interval_tree_iter_first(root, 0, ULONG_MAX);
+ if (!curr) {
+ /* No more ranges to combine */
+ break;
+ }
while (curr) {
if (prev) {
curr_gap = curr->start - prev->last;
@@ -975,6 +982,10 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
prev = curr;
curr = interval_tree_iter_next(curr, 0, ULONG_MAX);
}
+ if (!comb_start || !comb_end) {
+ /* No more ranges to combine */
+ break;
+ }
comb_start->last = comb_end->last;
interval_tree_remove(comb_end, root);
cur_nodes--;
--
2.34.1
While this may seem somewhat verbose, I am unsure how to refactor this function.
On Thu, 14 Sep 2023 17:08:39 +0800
Cong Liu <[email protected]> wrote:
> when compiling with smatch check, the following errors were encountered:
>
> drivers/vfio/vfio_main.c:957 vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
>
> this patch fix these error.
>
> Signed-off-by: Cong Liu <[email protected]>
> ---
> drivers/vfio/vfio_main.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 40732e8ed4c6..96d2f3030ebb 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -938,14 +938,17 @@ static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
> void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> u32 req_nodes)
> {
> - struct interval_tree_node *prev, *curr, *comb_start, *comb_end;
> + struct interval_tree_node *prev, *curr;
> + struct interval_tree_node *comb_start = NULL, *comb_end = NULL;
> unsigned long min_gap, curr_gap;
>
> /* Special shortcut when a single range is required */
> if (req_nodes == 1) {
> - unsigned long last;
> + unsigned long last = 0;
>
> comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
> + if (!comb_start)
> + return;
> curr = comb_start;
> while (curr) {
> last = curr->last;
@last no longer requires initialization with the @comb_start test.
However, all of these are testing for invalid parameters, which I think
we can eliminate if we simply introduce the following at the start of
the function:
if (!cur_nodes || cur_nodes <= req_nodes ||
WARN_ON(!req_nodes || !root->rb_root.rb_node))
return;
At that point we're guaranteed to have any entry for both the above and
below first entry and there must be at least a second entry (or a
driver bug telling us there are more entries than actually exist) for
the next call below. Thanks,
Alex
> @@ -963,6 +966,10 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> prev = NULL;
> min_gap = ULONG_MAX;
> curr = interval_tree_iter_first(root, 0, ULONG_MAX);
> + if (!curr) {
> + /* No more ranges to combine */
> + break;
> + }
> while (curr) {
> if (prev) {
> curr_gap = curr->start - prev->last;
> @@ -975,6 +982,10 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> prev = curr;
> curr = interval_tree_iter_next(curr, 0, ULONG_MAX);
> }
> + if (!comb_start || !comb_end) {
> + /* No more ranges to combine */
> + break;
> + }
> comb_start->last = comb_end->last;
> interval_tree_remove(comb_end, root);
> cur_nodes--;
when compiling with smatch check, the following errors were encountered:
drivers/vfio/vfio_main.c:957 vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
This patch initializes the variables last, comb_end, and comb_start
to avoid compiler warnings and add proper argument checks to ensure
interval_tree_iter_first() does not return NULL.
Signed-off-by: Cong Liu <[email protected]>
---
drivers/vfio/vfio_main.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 40732e8ed4c6..ecd4dd8e6b05 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -938,12 +938,17 @@ static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
u32 req_nodes)
{
- struct interval_tree_node *prev, *curr, *comb_start, *comb_end;
+ if (!cur_nodes || cur_nodes <= req_nodes ||
+ WARN_ON(!req_nodes || !root->rb_root.rb_node))
+ return;
+
+ struct interval_tree_node *prev, *curr;
+ struct interval_tree_node *comb_start = NULL, *comb_end = NULL;
unsigned long min_gap, curr_gap;
/* Special shortcut when a single range is required */
if (req_nodes == 1) {
- unsigned long last;
+ unsigned long last = 0;
comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
curr = comb_start;
--
2.34.1
On Wed, 20 Sep 2023 17:55:31 +0800
Cong Liu <[email protected]> wrote:
> when compiling with smatch check, the following errors were encountered:
>
> drivers/vfio/vfio_main.c:957 vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
> drivers/vfio/vfio_main.c:978 vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
>
> This patch initializes the variables last, comb_end, and comb_start
> to avoid compiler warnings and add proper argument checks to ensure
> interval_tree_iter_first() does not return NULL.
>
> Signed-off-by: Cong Liu <[email protected]>
> ---
> drivers/vfio/vfio_main.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 40732e8ed4c6..ecd4dd8e6b05 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -938,12 +938,17 @@ static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
> void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> u32 req_nodes)
> {
> - struct interval_tree_node *prev, *curr, *comb_start, *comb_end;
> + if (!cur_nodes || cur_nodes <= req_nodes ||
> + WARN_ON(!req_nodes || !root->rb_root.rb_node))
> + return;
Code should not precede variable declaration. The wrapped line should
align inside the parenthesis of the previous line.
> +
> + struct interval_tree_node *prev, *curr;
> + struct interval_tree_node *comb_start = NULL, *comb_end = NULL;
These only mask the issue reported by smatch, should we encounter the
condition where these are used uninitialized, derefencing NULL is only
marginally better.
> unsigned long min_gap, curr_gap;
>
> /* Special shortcut when a single range is required */
> if (req_nodes == 1) {
> - unsigned long last;
> + unsigned long last = 0;
This also masks the actual error, which can only occur from an empty
list which still results in a NULL pointer derefence. Should we even
make use of @last, a zero value is arbitrary.
I'll follow-up with a patch that I believe better resolves the report.
Thanks,
Alex
>
> comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
> curr = comb_start;
smatch reports:
vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
These errors are only reachable via invalid input, in the case of
@last when we receive an empty rb-tree or for @comb_{start,end} if the
rb-tree is empty or otherwise fails to produce a second node that
reduces the gap. Add tests with warnings for these cases.
Reported-by: Cong Liu <[email protected]>
Link: https://lore.kernel.org/all/[email protected]
Cc: Yishai Hadas <[email protected]>
Cc: Brett Creeley <[email protected]>
Signed-off-by: Alex Williamson <[email protected]>
---
drivers/vfio/vfio_main.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 40732e8ed4c6..e31e1952d7b8 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -946,6 +946,11 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
unsigned long last;
comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
+
+ /* Empty list */
+ if (WARN_ON_ONCE(!comb_start))
+ return;
+
curr = comb_start;
while (curr) {
last = curr->last;
@@ -975,6 +980,11 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
prev = curr;
curr = interval_tree_iter_next(curr, 0, ULONG_MAX);
}
+
+ /* Empty list or no nodes to combine */
+ if (WARN_ON_ONCE(min_gap == ULONG_MAX))
+ break;
+
comb_start->last = comb_end->last;
interval_tree_remove(comb_end, root);
cur_nodes--;
--
2.40.1
On 10/2/2023 3:43 PM, Alex Williamson wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>
>
> smatch reports:
>
> vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
> vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
> vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
>
> These errors are only reachable via invalid input, in the case of
> @last when we receive an empty rb-tree or for @comb_{start,end} if the
> rb-tree is empty or otherwise fails to produce a second node that
> reduces the gap. Add tests with warnings for these cases.
>
> Reported-by: Cong Liu <[email protected]>
> Link: https://lore.kernel.org/all/[email protected]
> Cc: Yishai Hadas <[email protected]>
> Cc: Brett Creeley <[email protected]>
> Signed-off-by: Alex Williamson <[email protected]>
> ---
> drivers/vfio/vfio_main.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 40732e8ed4c6..e31e1952d7b8 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -946,6 +946,11 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> unsigned long last;
>
> comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
> +
> + /* Empty list */
> + if (WARN_ON_ONCE(!comb_start))
> + return;
> +
> curr = comb_start;
> while (curr) {
> last = curr->last;
> @@ -975,6 +980,11 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> prev = curr;
> curr = interval_tree_iter_next(curr, 0, ULONG_MAX);
> }
> +
> + /* Empty list or no nodes to combine */
> + if (WARN_ON_ONCE(min_gap == ULONG_MAX))
> + break;
> +
> comb_start->last = comb_end->last;
> interval_tree_remove(comb_end, root);
> cur_nodes--;
> --
> 2.40.1
>
LGTM. Thanks for fixing this.
Reviewed-by: Brett Creeley <[email protected]>
On Mon, Oct 02, 2023 at 04:43:25PM -0600, Alex Williamson wrote:
> smatch reports:
>
> vfio_combine_iova_ranges() error: uninitialized symbol 'last'.
> vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_end'.
> vfio_combine_iova_ranges() error: potentially dereferencing uninitialized 'comb_start'.
>
> These errors are only reachable via invalid input, in the case of
> @last when we receive an empty rb-tree or for @comb_{start,end} if the
> rb-tree is empty or otherwise fails to produce a second node that
> reduces the gap. Add tests with warnings for these cases.
>
> Reported-by: Cong Liu <[email protected]>
> Link: https://lore.kernel.org/all/[email protected]
> Cc: Yishai Hadas <[email protected]>
> Cc: Brett Creeley <[email protected]>
> Signed-off-by: Alex Williamson <[email protected]>
> ---
> drivers/vfio/vfio_main.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
Yeah, this is much clearer
Reviewed-by: Jason Gunthorpe <[email protected]>
Thanks,
Jason