On Fri, Mar 9, 2018 at 10:10 PM, Miguel Ojeda <miguel.ojeda.sando...@gmail.com> wrote: > On Sat, Mar 10, 2018 at 4:11 AM, Randy Dunlap <rdun...@infradead.org> wrote: >> On 03/09/2018 04:07 PM, Andrew Morton wrote: >>> On Fri, 9 Mar 2018 12:05:36 -0800 Kees Cook <keesc...@chromium.org> wrote: >>> >>>> When max() is used in stack array size calculations from literal values >>>> (e.g. "char foo[max(sizeof(struct1), sizeof(struct2))]", the compiler >>>> thinks this is a dynamic calculation due to the single-eval logic, which >>>> is not needed in the literal case. This change removes several accidental >>>> stack VLAs from an x86 allmodconfig build: >>>> >>>> $ diff -u before.txt after.txt | grep ^- >>>> -drivers/input/touchscreen/cyttsp4_core.c:871:2: warning: ISO C90 forbids >>>> variable length array ‘ids’ [-Wvla] >>>> -fs/btrfs/tree-checker.c:344:4: warning: ISO C90 forbids variable length >>>> array ‘namebuf’ [-Wvla] >>>> -lib/vsprintf.c:747:2: warning: ISO C90 forbids variable length array >>>> ‘sym’ [-Wvla] >>>> -net/ipv4/proc.c:403:2: warning: ISO C90 forbids variable length array >>>> ‘buff’ [-Wvla] >>>> -net/ipv6/proc.c:198:2: warning: ISO C90 forbids variable length array >>>> ‘buff’ [-Wvla] >>>> -net/ipv6/proc.c:218:2: warning: ISO C90 forbids variable length array >>>> ‘buff64’ [-Wvla] >>>> >>>> Based on an earlier patch from Josh Poimboeuf. >>> >>> v1, v2 and v3 of this patch all fail with gcc-4.4.4: >>> >>> ./include/linux/jiffies.h: In function 'jiffies_delta_to_clock_t': >>> ./include/linux/jiffies.h:444: error: first argument to >>> '__builtin_choose_expr' not a constant >> >> >> I'm seeing that problem with >>> gcc --version >> gcc (SUSE Linux) 4.8.5 > > Same here, 4.8.5 fails. gcc 5.4.1 seems to work. I compiled a minimal > 5.1.0 and it seems to work as well.
And sparse freaks out too: drivers/net/ethernet/via/via-velocity.c:97:26: sparse: incorrect type in initializer (different address spaces) @@ expected void *addr @@ got struct mac_regs [noderef] <avoid *addr @@ drivers/net/ethernet/via/via-velocity.c:97:26: expected void *addr drivers/net/ethernet/via/via-velocity.c:97:26: got struct mac_regs [noderef] <asn:2>*mac_regs drivers/net/ethernet/via/via-velocity.c:100:49: sparse: incorrect type in argument 2 (different base types) @@ expected restricted pci_power_t [usertype] state @@ got _t [usertype] state @@ Alright, I'm giving up on fixing max(). I'll go back to STACK_MAX() or some other name for the simple macro. Bleh. -Kees -- Kees Cook Pixel Security
