FAILED: patch "[PATCH] crypto: Work around deallocated stack frame reference gcc bug" failed to apply to 4.11-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.11-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From d41519a69b35b10af7fda867fb9100df24fdf403 Mon Sep 17 00:00:00 2001
From: David Miller <davem@davemloft.net>
Date: Fri, 2 Jun 2017 11:28:54 -0400
Subject: [PATCH] crypto: Work around deallocated stack frame reference gcc bug
 on sparc.

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.

Cc: <stable@vger.kernel.org>
Reported-by: Anatoly Pugachev <matorola@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/infiniband/sw/rxe/rxe.h b/drivers/infiniband/sw/rxe/rxe.h
index ecdba2fce083..1ac5b8551a4d 100644
--- a/drivers/infiniband/sw/rxe/rxe.h
+++ b/drivers/infiniband/sw/rxe/rxe.h
@@ -68,6 +68,7 @@
 static inline u32 rxe_crc32(struct rxe_dev *rxe,
 			    u32 crc, void *next, size_t len)
 {
+	u32 retval;
 	int err;
 
 	SHASH_DESC_ON_STACK(shash, rxe->tfm);
@@ -81,7 +82,9 @@ static inline u32 rxe_crc32(struct rxe_dev *rxe,
 		return crc32_le(crc, next, len);
 	}
 
-	return *(u32 *)shash_desc_ctx(shash);
+	retval = *(u32 *)shash_desc_ctx(shash);
+	barrier_data(shash_desc_ctx(shash));
+	return retval;
 }
 
 int rxe_set_mtu(struct rxe_dev *rxe, unsigned int dev_mtu);
diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
index a97fdc156a03..baacc1866861 100644
--- a/fs/btrfs/hash.c
+++ b/fs/btrfs/hash.c
@@ -38,6 +38,7 @@ 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;
@@ -47,5 +48,7 @@ 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 2185c7a040a1..fd2e651bad6d 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1078,6 +1078,7 @@ 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;
@@ -1087,7 +1088,9 @@ 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 74a54b7f2562..9f79547d1b97 100644
--- a/lib/libcrc32c.c
+++ b/lib/libcrc32c.c
@@ -43,7 +43,7 @@ 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;
@@ -53,7 +53,9 @@ 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);