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From: lzhan011 <lzsx618@gmail.com>
To: nathan@kernel.org, nsc@kernel.org
Cc: rostedt@goodmis.org, linux-kbuild@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 9/9] tools/include: fix signed shift overflow in 32-bit unaligned accessors
Date: Mon,  5 Oct 2026 05:40:50 -0500	[thread overview]
Message-ID: <20261005104050.1786222-10-lzsx618@gmail.com> (raw)
In-Reply-To: <20261005104050.1786222-1-lzsx618@gmail.com>

From: lzhan011 <zhangleizhen645@gmail.com>

In __get_unaligned_le32() and __get_unaligned_be32() the most significant
byte is promoted to int before being shifted left by 24. If the byte is
0x80 or higher, the result does not fit in an int, which is undefined
behaviour. This happens for every kernel virtual address, e.g. in
sorttable, and UBSan reports:

  tools/include/tools/le_byteshift.h:14: runtime error: left shift of
  255 by 24 places cannot be represented in type 'int'

Cast the byte to uint32_t before shifting.

Fixes: a07f7672d7cf ("tools/include: Add byteshift headers for endian access")
Assisted-by: Claude:claude-opus-5-5 UBSan
Signed-off-by: lzhan011 <zhangleizhen645@gmail.com>
---
 tools/include/tools/be_byteshift.h | 2 +-
 tools/include/tools/le_byteshift.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/include/tools/be_byteshift.h b/tools/include/tools/be_byteshift.h
index f7d1d1698..2bda8d199 100644
--- a/tools/include/tools/be_byteshift.h
+++ b/tools/include/tools/be_byteshift.h
@@ -11,7 +11,7 @@ static inline uint16_t __get_unaligned_be16(const uint8_t *p)
 
 static inline uint32_t __get_unaligned_be32(const uint8_t *p)
 {
-	return p[0] << 24 | p[1] << 16 | p[2] << 8 | p[3];
+	return (uint32_t)p[0] << 24 | p[1] << 16 | p[2] << 8 | p[3];
 }
 
 static inline uint64_t __get_unaligned_be64(const uint8_t *p)
diff --git a/tools/include/tools/le_byteshift.h b/tools/include/tools/le_byteshift.h
index dc8565f39..e5c78a48a 100644
--- a/tools/include/tools/le_byteshift.h
+++ b/tools/include/tools/le_byteshift.h
@@ -11,7 +11,7 @@ static inline uint16_t __get_unaligned_le16(const uint8_t *p)
 
 static inline uint32_t __get_unaligned_le32(const uint8_t *p)
 {
-	return p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
+	return p[0] | p[1] << 8 | p[2] << 16 | (uint32_t)p[3] << 24;
 }
 
 static inline uint64_t __get_unaligned_le64(const uint8_t *p)
-- 
2.34.1


      parent reply	other threads:[~2026-10-05 10:41 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-05 10:40 [PATCH 0/9] kbuild: fix memory safety and UB bugs in host tools found by fuzzing lzhan011
2026-10-05 10:40 ` [PATCH 1/9] kconfig: fix NULL pointer dereference for defaults taken from choice members lzhan011
2026-10-08 16:04   ` Julian Braha
2026-10-05 10:40 ` [PATCH 2/9] genksyms: fix infinite loop on declarations with parameter lists lzhan011
2026-10-05 10:40 ` [PATCH 3/9] fixdep: fix out-of-bounds read on a comment ending with a backslash lzhan011
2026-10-05 10:40 ` [PATCH 4/9] kallsyms: do not call qsort() with a NULL table lzhan011
2026-10-05 10:40 ` [PATCH 5/9] modpost: fix stack out-of-bounds read for unterminated PNP ids lzhan011
2026-10-05 10:40 ` [PATCH 6/9] modpost: fix handling of short reads in read_text_file() lzhan011
2026-10-05 10:40 ` [PATCH 7/9] modpost: fix pointer arithmetic on NULL in parse_source_files() lzhan011
2026-10-05 10:40 ` [PATCH 8/9] sorttable: avoid pointer arithmetic overflow when locating sort_needed lzhan011
2026-10-05 10:40 ` lzhan011 [this message]

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