| Message ID | ZRsUL/hATNruwtla@work |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,next] PCI/P2PDMA: Fix potential undefined behavior bug in struct pci_p2pdma_pagemap | expand |
On Mon, Oct 02, 2023 at 09:04:15PM +0200, Gustavo A. R. Silva wrote: > `struct dev_pagemap` is a flexible structure, which means that it > contains a flexible-array member at the bottom. This could potentially > lead to an overwrite of the objects following `pgmap` in `struct > pci_p2pdma_pagemap`, when `nr_range > 1`. This is currently not the > case (notice that `nr_range` is hardcoded to `1`), however as commit > b7b3c01b1915 ("mm/memremap_pages: support multiple ranges per invocation") > mentions in the subject line, this code can `support multiple > ranges per invocation`. So, we'd better prevent any problems that may > arise in the future. > > Fix this by placing the declaration of object `pgmap` at the end of > `struct pci_p2pdma_pagemap`. > > -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting > ready to enable it globally. > > Reviewed-by: Logan Gunthorpe <logang@deltatee.com> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Applied to pci/p2pdma for v6.7. Since it's not a current problem, I assume there's no reason to apply it for v6.6 (or tag it for stable); let me know if otherwise. > --- > Changes in v2: > - Remove `Fixes:` tags. (Logan Gunthorpe) > - Update changelog text. Make it clear that `nr_range` is hardcoded to `1` > (Logan Gunthorpe) > - Update subject. > - Add Logan's RB. > > v1: > Link: https://lore.kernel.org/linux-hardening/ZRnf6wVOu0IJQ2Ok@work/ > > drivers/pci/p2pdma.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index fa7370f9561a..ab34d3d36a64 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -28,9 +28,9 @@ struct pci_p2pdma { > }; > > struct pci_p2pdma_pagemap { > - struct dev_pagemap pgmap; > struct pci_dev *provider; > u64 bus_offset; > + struct dev_pagemap pgmap; > }; > > static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap) > -- > 2.34.1 >
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index fa7370f9561a..ab34d3d36a64 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -28,9 +28,9 @@ struct pci_p2pdma { }; struct pci_p2pdma_pagemap { - struct dev_pagemap pgmap; struct pci_dev *provider; u64 bus_offset; + struct dev_pagemap pgmap; }; static struct pci_p2pdma_pagemap *to_p2p_pgmap(struct dev_pagemap *pgmap)
`struct dev_pagemap` is a flexible structure, which means that it contains a flexible-array member at the bottom. This could potentially lead to an overwrite of the objects following `pgmap` in `struct pci_p2pdma_pagemap`, when `nr_range > 1`. This is currently not the case (notice that `nr_range` is hardcoded to `1`), however as commit b7b3c01b1915 ("mm/memremap_pages: support multiple ranges per invocation") mentions in the subject line, this code can `support multiple ranges per invocation`. So, we'd better prevent any problems that may arise in the future. Fix this by placing the declaration of object `pgmap` at the end of `struct pci_p2pdma_pagemap`. -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting ready to enable it globally. Reviewed-by: Logan Gunthorpe <logang@deltatee.com> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- Changes in v2: - Remove `Fixes:` tags. (Logan Gunthorpe) - Update changelog text. Make it clear that `nr_range` is hardcoded to `1` (Logan Gunthorpe) - Update subject. - Add Logan's RB. v1: Link: https://lore.kernel.org/linux-hardening/ZRnf6wVOu0IJQ2Ok@work/ drivers/pci/p2pdma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)