From 3947a03066051482ed4ca7ac34aea4a86c4d8a92 Mon Sep 17 00:00:00 2001 From: David Miller Date: Fri, 2 Jun 2017 11:28:54 -0400 Subject: [PATCH] crypto: Work around deallocated stack frame reference gcc bug on sparc. commit d41519a69b35b10af7fda867fb9100df24fdf403 upstream. On sparc, if we have an alloca() like situation, as is the case with SHASH_DESC_ON_STACK(), we can end up referencing deallocated stack memory. The result can be that the value is clobbered if a trap or interrupt arrives at just the right instruction. It only occurs if the function ends returning a value from that alloca() area and that value can be placed into the return value register using a single instruction. For example, in lib/libcrc32c.c:crc32c() we end up with a return sequence like: return %i7+8 lduw [%o5+16], %o0 ! MEM[(u32 *)__shash_desc.1_10 + 16B], %o5 holds the base of the on-stack area allocated for the shash descriptor. But the return released the stack frame and the register window. So if an intererupt arrives between 'return' and 'lduw', then the value read at %o5+16 can be corrupted. Add a data compiler barrier to work around this problem. This is exactly what the gcc fix will end up doing as well, and it absolutely should not change the code generated for other cpus (unless gcc on them has the same bug :-) With crucial insight from Eric Sandeen. Reported-by: Anatoly Pugachev Signed-off-by: David S. Miller Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/hash.c | 5 ++++- fs/f2fs/f2fs.h | 5 ++++- lib/libcrc32c.c | 6 ++++-- 3 files changed, 12 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c index aae520b2aee5..6fc94fcba072 100644 --- a/fs/btrfs/hash.c +++ b/fs/btrfs/hash.c @@ -33,6 +33,7 @@ u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length) { SHASH_DESC_ON_STACK(shash, tfm); u32 *ctx = (u32 *)shash_desc_ctx(shash); + u32 retval; int err; shash->tfm = tfm; @@ -42,5 +43,7 @@ u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length) err = crypto_shash_update(shash, address, length); BUG_ON(err); - return *ctx; + retval = *ctx; + barrier_data(ctx); + return retval; } diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index dd840f60e172..c1a0aef8efc6 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -1268,6 +1268,7 @@ static inline u32 f2fs_crc32(struct f2fs_sb_info *sbi, const void *address, { SHASH_DESC_ON_STACK(shash, sbi->s_chksum_driver); u32 *ctx = (u32 *)shash_desc_ctx(shash); + u32 retval; int err; shash->tfm = sbi->s_chksum_driver; @@ -1277,7 +1278,9 @@ static inline u32 f2fs_crc32(struct f2fs_sb_info *sbi, const void *address, err = crypto_shash_update(shash, address, length); BUG_ON(err); - return *ctx; + retval = *ctx; + barrier_data(ctx); + return retval; } static inline bool f2fs_crc_valid(struct f2fs_sb_info *sbi, __u32 blk_crc, diff --git a/lib/libcrc32c.c b/lib/libcrc32c.c index acf9da449f81..2c573f08adb7 100644 --- a/lib/libcrc32c.c +++ b/lib/libcrc32c.c @@ -42,7 +42,7 @@ static struct crypto_shash *tfm; u32 crc32c(u32 crc, const void *address, unsigned int length) { SHASH_DESC_ON_STACK(shash, tfm); - u32 *ctx = (u32 *)shash_desc_ctx(shash); + u32 ret, *ctx = (u32 *)shash_desc_ctx(shash); int err; shash->tfm = tfm; @@ -52,7 +52,9 @@ u32 crc32c(u32 crc, const void *address, unsigned int length) err = crypto_shash_update(shash, address, length); BUG_ON(err); - return *ctx; + ret = *ctx; + barrier_data(ctx); + return ret; } EXPORT_SYMBOL(crc32c);