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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753723556; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4gcMDGkU7vR5AmGFsCSLxqFiamRKfDfSNEO0CvHrKl4=; b=Q2DQLSKB4xc8v57dNZGZoOBqqEH/MM891E3nucd+yonptWIwX+FC9i9X7RrMM4c9LZHLsN qJDGdITkQFZ8OUceZK9opidNu4t4GH5kLZc3lA1e6lo+BBi0xUehhtc6K9HfOcXdjndGLI qB7veSXBJBvo65LILdVICEkqVSH1HRg= X-MC-Unique: q2b8ltdtPNORrP47y2B3-Q-1 X-Mimecast-MFC-AGG-ID: q2b8ltdtPNORrP47y2B3-Q_1753723551 From: Thomas Huth To: qemu-devel@nongnu.org, Paolo Bonzini , Peter Xu , David Hildenbrand Cc: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [PATCH] system/physmem: Silence warning from ubsan Date: Mon, 28 Jul 2025 19:25:45 +0200 Message-ID: <20250728172545.314178-1-thuth@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" From: Thomas Huth When compiling QEMU with --enable-ubsan there is a undefined behavior warning when running the bios-tables-test for example: .../system/physmem.c:3243:13: runtime error: applying non-zero offset 2621= 44 to null pointer #0 0x55ac1df5fbc4 in address_space_write_rom_internal .../system/physme= m.c:3243:13 The problem is that buf is indeed NULL if the function is e.g. called with type =3D=3D FLUSH_CACHE. Add a check to fix the issue. Signed-off-by: Thomas Huth Reviewed-by: David Hildenbrand --- system/physmem.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/system/physmem.c b/system/physmem.c index 130c148ffb5..00333ffa7f7 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -3240,8 +3240,10 @@ static inline MemTxResult address_space_write_rom_in= ternal(AddressSpace *as, } } len -=3D l; - buf +=3D l; addr +=3D l; + if (buf) { + buf +=3D l; + } } return MEMTX_OK; } --=20 2.50.1