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From: Dan Carpenter <dan.carpenter@oracle.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [PATCH] XArray: Fix a math problem in xa_is_err()
Date: Tue, 15 Jan 2019 22:52:41 +0300	[thread overview]
Message-ID: <20190115195241.GB1074@kadam> (raw)

There is a math problem here which leads to a lot of static checker
warnings for me:

net/sunrpc/clnt.c:451 rpc_new_client() error: (-4096) too low for ERR_PTR

Error values are from -1 to -4095 or from 0xffffffff to 0xfffff001 in
hexadecimal.  (I am assuming a 32 bit system for simplicity).  We are
using the lowest two bits to hold some internal XArray data so the
error is shifted two spaces to the left.  0xfffff001 << 2 is 0xffffc004.
And finally we want to check that BIT(1) is set so we add 2 which gives
us 0xffffc006.

In other words, we should be checking that "entry >= 0xffffc006", but
the check is actually testing if "entry >= 0xffffc002".

Fixes: 76b4e5299565 ("XArray: Permit storing 2-byte-aligned pointers")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 include/linux/xarray.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 12244aa98a69..4208042f939a 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -177,7 +177,8 @@ static inline bool xa_is_internal(const void *entry)
 static inline bool xa_is_err(const void *entry)
 {
 	return unlikely(xa_is_internal(entry) &&
-			(unsigned long)entry >= -((MAX_ERRNO << 2) + 2));
+			(unsigned long)entry >=
+				(((unsigned long)(-MAX_ERRNO << 2) + 2)));
 }
 
 /**
-- 
2.17.1


WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [PATCH] XArray: Fix a math problem in xa_is_err()
Date: Tue, 15 Jan 2019 19:52:41 +0000	[thread overview]
Message-ID: <20190115195241.GB1074@kadam> (raw)

There is a math problem here which leads to a lot of static checker
warnings for me:

net/sunrpc/clnt.c:451 rpc_new_client() error: (-4096) too low for ERR_PTR

Error values are from -1 to -4095 or from 0xffffffff to 0xfffff001 in
hexadecimal.  (I am assuming a 32 bit system for simplicity).  We are
using the lowest two bits to hold some internal XArray data so the
error is shifted two spaces to the left.  0xfffff001 << 2 is 0xffffc004.
And finally we want to check that BIT(1) is set so we add 2 which gives
us 0xffffc006.

In other words, we should be checking that "entry >= 0xffffc006", but
the check is actually testing if "entry >= 0xffffc002".

Fixes: 76b4e5299565 ("XArray: Permit storing 2-byte-aligned pointers")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 include/linux/xarray.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 12244aa98a69..4208042f939a 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -177,7 +177,8 @@ static inline bool xa_is_internal(const void *entry)
 static inline bool xa_is_err(const void *entry)
 {
 	return unlikely(xa_is_internal(entry) &&
-			(unsigned long)entry >= -((MAX_ERRNO << 2) + 2));
+			(unsigned long)entry >+				(((unsigned long)(-MAX_ERRNO << 2) + 2)));
 }
 
 /**
-- 
2.17.1

             reply	other threads:[~2019-01-15 19:53 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-15 19:52 Dan Carpenter [this message]
2019-01-15 19:52 ` [PATCH] XArray: Fix a math problem in xa_is_err() Dan Carpenter
2019-01-15 21:07 ` Matthew Wilcox
2019-01-15 21:07   ` Matthew Wilcox
2019-01-15 21:35   ` Dan Carpenter
2019-01-15 21:35     ` Dan Carpenter

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