From f0fe77f601c3d6a821198f88f7adb0a05b8fe03e Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 11 Oct 2018 13:06:17 +0200 Subject: lib/bch: fix possible stack overrun The previous patch introduced very large kernel stack usage and a Makefile change to hide the warning about it. From what I can tell, a number of things went wrong here: - The BCH_MAX_T constant was set to the maximum value for 'n', not the maximum for 't', which is much smaller. - The stack usage is actually larger than the entire kernel stack on some architectures that can use 4KB stacks (m68k, sh, c6x), which leads to an immediate overrun. - The justification in the patch description claimed that nothing changed, however that is not the case even without the two points above: the configuration is machine specific, and most boards never use the maximum BCH_ECC_WORDS() length but instead have something much smaller. That maximum would only apply to machines that use both the maximum block size and the maximum ECC strength. The largest value for 't' that I could find is '32', which in turn leads to a 60 byte array instead of 2048 bytes. Making it '64' for future extension seems also worthwhile, with 120 bytes for the array. Anything larger won't fit into the OOB area on NAND flash. With that changed, the warning can be enabled again. Only linux-4.19+ contains the breakage, so this is only needed as a stable backport if it does not make it into the release. Fixes: 02361bc77888 ("lib/bch: Remove VLA usage") Reported-by: Ard Biesheuvel Cc: stable@vger.kernel.org Signed-off-by: Arnd Bergmann Signed-off-by: Boris Brezillon --- lib/Makefile | 1 - 1 file changed, 1 deletion(-) (limited to 'lib/Makefile') diff --git a/lib/Makefile b/lib/Makefile index ca3f7ebb900d..423876446810 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -119,7 +119,6 @@ obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/ obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/ obj-$(CONFIG_REED_SOLOMON) += reed_solomon/ obj-$(CONFIG_BCH) += bch.o -CFLAGS_bch.o := $(call cc-option,-Wframe-larger-than=4500) obj-$(CONFIG_LZO_COMPRESS) += lzo/ obj-$(CONFIG_LZO_DECOMPRESS) += lzo/ obj-$(CONFIG_LZ4_COMPRESS) += lz4/ -- cgit