[PATCH 3.12 034/155] LZ4 : fix the data abort issue

[Jiri Slaby]

From: JeHyeon Yeon <tom.yeon@xxxxxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit d5e7cafd69da24e6d6cc988fab6ea313a2577efc upstream.

If the part of the compression data are corrupted, or the compression
data is totally fake, the memory access over the limit is possible.

This is the log from my system usning lz4 decompression.
   [6502]data abort, halting
   [6503]r0  0x00000000 r1  0x00000000 r2  0xdcea0ffc r3  0xdcea0ffc
   [6509]r4  0xb9ab0bfd r5  0xdcea0ffc r6  0xdcea0ff8 r7  0xdce80000
   [6515]r8  0x00000000 r9  0x00000000 r10 0x00000000 r11 0xb9a98000
   [6522]r12 0xdcea1000 usp 0x00000000 ulr 0x00000000 pc  0x820149bc
   [6528]spsr 0x400001f3
and the memory addresses of some variables at the moment are
    ref:0xdcea0ffc, op:0xdcea0ffc, oend:0xdcea1000

As you can see, COPYLENGH is 8bytes, so @ref and @op can access the momory
over @oend.

Signed-off-by: JeHyeon Yeon <tom.yeon@xxxxxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 lib/lz4/lz4_decompress.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/lz4/lz4_decompress.c b/lib/lz4/lz4_decompress.c
index 7a85967060a5..f0f5c5c3de12 100644
--- a/lib/lz4/lz4_decompress.c
+++ b/lib/lz4/lz4_decompress.c
@@ -139,6 +139,9 @@ static int lz4_uncompress(const char *source, char *dest, int osize)
 			/* Error: request to write beyond destination buffer */
 			if (cpy > oend)
 				goto _output_error;
+			if ((ref + COPYLENGTH) > oend ||
+					(op + COPYLENGTH) > oend)
+				goto _output_error;
 			LZ4_SECURECOPY(ref, op, (oend - COPYLENGTH));
 			while (op < cpy)
 				*op++ = *ref++;
-- 
2.3.4

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