From: Rasmus Villemoes linux@rasmusvillemoes.dk
[ Upstream commit 942859d969de7f6f7f2659a79237a758b42782da ]
snprintf() should be given the full buffer size, not one less. And it guarantees nul-termination, so doing it manually afterwards is pointless.
It's even potentially harmful (though probably not in practice because CPER_REC_LEN is 256), due to the "return how much would have been written had the buffer been big enough" semantics. I.e., if the bank and/or device strings are long enough that the "DIMM location ..." output gets truncated, writing to msg[n] is a buffer overflow.
Signed-off-by: Rasmus Villemoes linux@rasmusvillemoes.dk Fixes: 3760cd20402d4 ("CPER: Adjust code flow of some functions") Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/efi/cper.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/firmware/efi/cper.c b/drivers/firmware/efi/cper.c index b1af0de2e100..e48298687b76 100644 --- a/drivers/firmware/efi/cper.c +++ b/drivers/firmware/efi/cper.c @@ -263,8 +263,7 @@ static int cper_dimm_err_location(struct cper_mem_err_compact *mem, char *msg) if (!msg || !(mem->validation_bits & CPER_MEM_VALID_MODULE_HANDLE)) return 0;
- n = 0; - len = CPER_REC_LEN - 1; + len = CPER_REC_LEN; dmi_memdev_name(mem->mem_dev_handle, &bank, &device); if (bank && device) n = snprintf(msg, len, "DIMM location: %s %s ", bank, device); @@ -273,7 +272,6 @@ static int cper_dimm_err_location(struct cper_mem_err_compact *mem, char *msg) "DIMM location: not present. DMI handle: 0x%.4x ", mem->mem_dev_handle);
- msg[n] = '\0'; return n; }