Messages in this thread | | | Subject | Re: [PATCH v2] powerpc/64: Fix build failure with GCC 8.1 | From | Christophe LEROY <> | Date | Tue, 29 May 2018 10:56:31 +0200 |
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Le 29/05/2018 à 09:47, Geert Uytterhoeven a écrit : > Hi Christophe, > > CC Geoff > > On Tue, May 29, 2018 at 8:03 AM, Christophe Leroy > <christophe.leroy@c-s.fr> wrote: >> CC arch/powerpc/kernel/nvram_64.o >> arch/powerpc/kernel/nvram_64.c: In function 'nvram_create_partition': >> arch/powerpc/kernel/nvram_64.c:1042:2: error: 'strncpy' specified bound 12 equals destination size [-Werror=stringop-truncation] >> strncpy(new_part->header.name, name, 12); >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> CC arch/powerpc/kernel/trace/ftrace.o >> In function 'make_field', >> inlined from 'ps3_repository_read_boot_dat_address' at arch/powerpc/platforms/ps3/repository.c:900:9: >> arch/powerpc/platforms/ps3/repository.c:106:2: error: 'strncpy' output truncated before terminating nul copying 8 bytes from a string of the same length [-Werror=stringop-truncation] >> strncpy((char *)&n, text, 8); >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > > Thanks for your patch! > >> --- a/arch/powerpc/kernel/nvram_64.c >> +++ b/arch/powerpc/kernel/nvram_64.c >> @@ -1039,7 +1039,7 @@ loff_t __init nvram_create_partition(const char *name, int sig, >> new_part->index = free_part->index; >> new_part->header.signature = sig; >> new_part->header.length = size; >> - strncpy(new_part->header.name, name, 12); >> + memcpy(new_part->header.name, name, strnlen(name, sizeof(new_part->header.name))); > > The comment for nvram_header.lgnth says: > > /* Terminating null required only for names < 12 chars. */ > > This will not terminate the string with a zero (the struct is > allocated with kmalloc). > So the original code is correct, the new one isn't.
Right, then I have to first zeroize the destination.
> >> new_part->header.checksum = nvram_checksum(&new_part->header); >> >> rc = nvram_write_header(new_part); >> diff --git a/arch/powerpc/platforms/ps3/repository.c b/arch/powerpc/platforms/ps3/repository.c >> index 50dbaf24b1ee..e49c887787c4 100644 >> --- a/arch/powerpc/platforms/ps3/repository.c >> +++ b/arch/powerpc/platforms/ps3/repository.c >> @@ -101,9 +101,9 @@ static u64 make_first_field(const char *text, u64 index) >> >> static u64 make_field(const char *text, u64 index) >> { >> - u64 n; >> + u64 n = 0; >> >> - strncpy((char *)&n, text, 8); >> + memcpy((char *)&n, text, strnlen(text, sizeof(n))); > > This changes behavior: strncpy() fills the remainder of the buffer with > zeroes. I don't remember the details of the PS3 repository structure, > but given this writes to a fixed size u64 buffer, I'd expect the PS3 > hypervisor code to (1) rely on the zero padding, and (2) not need a zero > terminator if there are 8 characters in the buffer, so probably the > original code is correct, and the "fixed" code isn't.
Here I have set n to 0 prior to the copy, so the buffer IS zero padded.
Christophe
> > Has this been tested on a PS3? > >> return n + index; >> } > > Gr{oetje,eeting}s, > > Geert >
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