linux-ext4 - [PATCH 3/8] e2fsck/pass1.c: Fix undefined behavior in check

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Message-ID: <20121213220415.GK9713@sli.dy.fi>
Date:	Fri, 14 Dec 2012 00:04:15 +0200
From:	Sami Liedes <sami.liedes@....fi>
To:	linux-ext4@...r.kernel.org
Subject: [PATCH 3/8] e2fsck/pass1.c: Fix undefined behavior in check_blocks()

The offending code is this:

   pb.max_blocks = 1 << (31 - fs->super->s_log_block_size);

While pb.max_blocks is of type blk64_t, the intermediate result of the
expression '1 << 31' is int. However 1 << 31 does not fit in a 32-bit
signed int, causing undefined behavior.

Caught using clang -fsanitize=undefined.

Signed-off-by: Sami Liedes <sami.liedes@....fi>
---
 e2fsck/pass1.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index a4bd956..9cd8832 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -2095,7 +2095,7 @@ static void check_blocks(e2fsck_t ctx, struct problem_context *pctx,
 	pb.previous_block = 0;
 	pb.is_dir = LINUX_S_ISDIR(inode->i_mode);
 	pb.is_reg = LINUX_S_ISREG(inode->i_mode);
-	pb.max_blocks = 1 << (31 - fs->super->s_log_block_size);
+	pb.max_blocks = ((blk64_t)1) << (31 - fs->super->s_log_block_size);
 	pb.inode = inode;
 	pb.pctx = pctx;
 	pb.ctx = ctx;
-- 
1.7.10.4
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