[PATCH 5/6] treewide: remove dereference of list iterator after loop body

Jakob Koschel
2022-02-28T11:09:39Z

The list iterator variable will be a bogus pointer if no break was hit.
Dereferencing it could load *any* out-of-bounds/undefined value
making it unsafe to use that in the comparision to determine if the
specific element was found.

This is fixed by using a separate list iterator variable for the loop
and only setting the original variable if a suitable element was found.
Then determing if the element was found is simply checking if the
variable is set.

Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
---
drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c | 11 +++++++----
drivers/scsi/wd719x.c | 12 ++++++++----
fs/f2fs/segment.c | 9 ++++++---
3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c
index 57199be082fd..c56cd9e59a66 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c
@@ -471,20 +471,23 @@ nvkm_pstate_new(struct nvkm_clk *clk, int idx)
static int
nvkm_clk_ustate_update(struct nvkm_clk *clk, int req)
{
- struct nvkm_pstate *pstate;
+ struct nvkm_pstate *pstate = NULL;
+ struct nvkm_pstate *tmp;
int i = 0;

if (!clk->allow_reclock)
return -ENOSYS;

if (req != -1 && req != -2) {
- list_for_each_entry(pstate, &clk->states, head) {
- if (pstate->pstate == req)
+ list_for_each_entry(tmp, &clk->states, head) {
+ if (tmp->pstate == req) {
+ pstate = tmp;
break;
+ }
i++;
}

- if (pstate->pstate != req)
+ if (!pstate)
return -EINVAL;
req = i;
}
diff --git a/drivers/scsi/wd719x.c b/drivers/scsi/wd719x.c
index 1a7947554581..be270ed8e00d 100644
--- a/drivers/scsi/wd719x.c
+++ b/drivers/scsi/wd719x.c
@@ -684,11 +684,15 @@ static irqreturn_t wd719x_interrupt(int irq, void *dev_id)
case WD719X_INT_SPIDERFAILED:
/* was the cmd completed a direct or SCB command? */
if (regs.bytes.OPC == WD719X_CMD_PROCESS_SCB) {
- struct wd719x_scb *scb;
- list_for_each_entry(scb, &wd->active_scbs, list)
- if (SCB_out == scb->phys)
+ struct wd719x_scb *scb = NULL;
+ struct wd719x_scb *tmp;
+
+ list_for_each_entry(tmp, &wd->active_scbs, list)
+ if (SCB_out == tmp->phys) {
+ scb = tmp;
break;
- if (SCB_out == scb->phys)
+ }
+ if (scb)
wd719x_interrupt_SCB(wd, regs, scb);
else
dev_err(&wd->pdev->dev, "card returned invalid SCB pointer\n");
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 1dabc8244083..a3684385e04a 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -356,16 +356,19 @@ void f2fs_drop_inmem_page(struct inode *inode, struct page *page)
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct list_head *head = &fi->inmem_pages;
struct inmem_pages *cur = NULL;
+ struct inmem_pages *tmp;

f2fs_bug_on(sbi, !page_private_atomic(page));

mutex_lock(&fi->inmem_lock);
- list_for_each_entry(cur, head, list) {
- if (cur->page == page)
+ list_for_each_entry(tmp, head, list) {
+ if (tmp->page == page) {
+ cur = tmp;
break;
+ }
}

- f2fs_bug_on(sbi, list_empty(head) || cur->page != page);
+ f2fs_bug_on(sbi, !cur);
list_del(&cur->list);
mutex_unlock(&fi->inmem_lock);

--
2.25.1