| Message ID | 3e37f05c7593f1016f0a46de188b3357cbbd0c0b.1695060389.git.christophe.jaillet@wanadoo.fr |
|---|---|
| State | New |
| Headers | show |
| Series | udmabuf: Fix a potential (and unlikely) access to unallocated memory | expand |
Le 18/09/2023 à 05:10, Gustavo A. R. Silva a écrit : > > > On 9/18/23 12:46, Christophe JAILLET wrote: >> If 'list_limit' is set to a very high value, 'lsize' computation could >> overflow if 'head.count' is big enough. >> >> In such a case, udmabuf_create() will access to memory beyond 'list'. >> >> Use size_mul() to saturate the value, and have memdup_user() fail. >> >> Fixes: fbb0de795078 ("Add udmabuf misc device") >> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> >> --- >> drivers/dma-buf/udmabuf.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c >> index c40645999648..fb4c4b5b3332 100644 >> --- a/drivers/dma-buf/udmabuf.c >> +++ b/drivers/dma-buf/udmabuf.c >> @@ -314,13 +314,13 @@ static long udmabuf_ioctl_create_list(struct >> file *filp, unsigned long arg) >> struct udmabuf_create_list head; >> struct udmabuf_create_item *list; >> int ret = -EINVAL; >> - u32 lsize; >> + size_t lsize; >> if (copy_from_user(&head, (void __user *)arg, sizeof(head))) >> return -EFAULT; >> if (head.count > list_limit) >> return -EINVAL; >> - lsize = sizeof(struct udmabuf_create_item) * head.count; >> + lsize = size_mul(sizeof(struct udmabuf_create_item), head.count); >> list = memdup_user((void __user *)(arg + sizeof(head)), lsize); >> if (IS_ERR(list)) >> return PTR_ERR(list); > > How about this, and we get rid of `lsize`: Keeping or removing lsize is mostly a matter of taste, I think. Using sizeof(*list) is better. Let see if there are some other comments, and I'll send a v2. Thanks for the feed-back. CJ > > diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c > index c40645999648..5cf9d849aaa8 100644 > --- a/drivers/dma-buf/udmabuf.c > +++ b/drivers/dma-buf/udmabuf.c > @@ -314,14 +314,13 @@ static long udmabuf_ioctl_create_list(struct file > *filp, unsigned long arg) > struct udmabuf_create_list head; > struct udmabuf_create_item *list; > int ret = -EINVAL; > - u32 lsize; > > if (copy_from_user(&head, (void __user *)arg, sizeof(head))) > return -EFAULT; > if (head.count > list_limit) > return -EINVAL; > - lsize = sizeof(struct udmabuf_create_item) * head.count; > - list = memdup_user((void __user *)(arg + sizeof(head)), lsize); > + list = memdup_user((void __user *)(arg + sizeof(head)), > + size_mul(sizeof(*list), head.count)); > if (IS_ERR(list)) > return PTR_ERR(list); > > > -- > Gustavo >
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index c40645999648..fb4c4b5b3332 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -314,13 +314,13 @@ static long udmabuf_ioctl_create_list(struct file *filp, unsigned long arg) struct udmabuf_create_list head; struct udmabuf_create_item *list; int ret = -EINVAL; - u32 lsize; + size_t lsize; if (copy_from_user(&head, (void __user *)arg, sizeof(head))) return -EFAULT; if (head.count > list_limit) return -EINVAL; - lsize = sizeof(struct udmabuf_create_item) * head.count; + lsize = size_mul(sizeof(struct udmabuf_create_item), head.count); list = memdup_user((void __user *)(arg + sizeof(head)), lsize); if (IS_ERR(list)) return PTR_ERR(list);
If 'list_limit' is set to a very high value, 'lsize' computation could overflow if 'head.count' is big enough. In such a case, udmabuf_create() will access to memory beyond 'list'. Use size_mul() to saturate the value, and have memdup_user() fail. Fixes: fbb0de795078 ("Add udmabuf misc device") Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- drivers/dma-buf/udmabuf.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)