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Tue, 26 Jan 2021 05:08:03 +0000 (GMT) From: "Namjae Jeon" To: "'Matthew Wilcox'" Cc: , , , , "'syzbot'" In-Reply-To: Subject: RE: UBSAN: shift-out-of-bounds in exfat_fill_super Date: Tue, 26 Jan 2021 14:08:03 +0900 Message-ID: <052101d6f3a1$3997c420$acc74c60$@samsung.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQKx/jOXwjWHcb1Mo6E7TSXbn6EBcQJApmhQAe65oTeoYcKoMIAAB+GA Content-Language: ko X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFuphk+LIzCtJLcpLzFFi42LZdlhTX3fLYv4Eg7W2Fnv2nmSxuLxrDpvF ln9HWC3uXWe0uLFlLrPF7x9z2BzYPPZMPMnmsXmFlkffllWMHjPfqnl83iQXwBqVY5ORmpiS WqSQmpecn5KZl26r5B0c7xxvamZgqGtoaWGupJCXmJtqq+TiE6DrlpkDtF1JoSwxpxQoFJBY XKykb2dTlF9akqqQkV9cYquUWpCSU2BoUKBXnJhbXJqXrpecn2tlaGBgZApUmZCT0fblBWvB BfaKO7cfMDcwrmbtYuTgkBAwkTix36qLkYtDSGAHo0TTkevsEM4nRollu/cyQTjfGCWW3mpn gemY+54DIr6XUaJ5zzpGCOclo8Sn7p9sXYycHGwCuhL//uwHs0UEdCS6Xm5nBSliFjjBKHHl zmmw3ZwCvBIT/lmD1AgLWEtMebobrJ5FQFVi3+0GdhCbV8BSYuGtaYwQtqDEyZlPWEBsZgF5 ie1v5zCD2BICChI/ny5jhdjlJnF49kmoGhGJ2Z1tUDVTOSSWveSEsF0kZjy+ywphC0u8Or6F HcKWknjZ38YO8WS1xMf9UK0djBIvvttC2MYSN9dvALueWUBTYv0ufYiwosTO33MZIbbySbz7 2gMNXF6JjjYhiBJVib5Lh5kgbGmJrvYP7BMYlWYh+WsWkr9mIbl/FsKyBYwsqxjFUguKc9NT iw0LTJFjehMjOFlqWe5gnP72g94hRiYOxkOMEhzMSiK8u/V4EoR4UxIrq1KL8uOLSnNSiw8x mgJDeiKzlGhyPjBd55XEG5oaGRsbW5iYmZuZGiuJ8yYZPIgXEkhPLEnNTk0tSC2C6WPi4JRq YCpKWnH34p3Kxjm1zvnGi7oux+ulWyRE35I/175ijdr0U4vjzzxUTpi0qM2gfwOvmc3dyUmq jYJBBjarF56pWCjIu89Cadu3JUuqVFJfSzZ5XpabdPp+EBNj0n/rKO50h+i7Ezq267+eHX0i yPukxuapggal292YoiotXJ6/NXs7/16dSeVu8/2R5VHPt7lMmhbTHlbdMXPZ3VKmh2fPpN59 ax+bs5/Hv4V3sXOoQ0L2HSab77wp+ldUz+jdKDzc4BiZYp4i81rwZo1tCP+7d6XnFor6dh2q 4FS8c8lR/uTarKkbj73bGJWu0riL76R5otjVia+PVTziZir137n/2Ycgx0mxD65mmFz2uPxr jRJLcUaioRZzUXEiAKDGeHwfBAAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrBLMWRmVeSWpSXmKPExsWy7bCSnO7mxfwJBlNfyFjs2XuSxeLyrjls Flv+HWG1uHed0eLGlrnMFr9/zGFzYPPYM/Ekm8fmFVoefVtWMXrMfKvm8XmTXABrFJdNSmpO Zllqkb5dAldG25cXrAUX2Cvu3H7A3MC4mrWLkYNDQsBEYu57ji5GLg4hgd2MEr8/f2DqYuQE iktLHDtxhhmiRlji8OFiiJrnjBJXWjcxg9SwCehK/Puznw3EFhHQkeh6uZ0VpIhZ4AyjxPeu 6ywQHdsZJTp+/WEHmcQpwCsx4Z81SIOwgLXElKe7wZpZBFQl9t1uYAexeQUsJRbemsYIYQtK nJz5hAWklVlAT6JtI1iYWUBeYvvbOcwQdypI/Hy6jBXiBjeJw7NPskDUiEjM7mxjnsAoPAvJ pFkIk2YhmTQLSccCRpZVjJKpBcW56bnFhgWGeanlesWJucWleel6yfm5mxjBkaOluYNx+6oP eocYmTgYDzFKcDArifDu1uNJEOJNSaysSi3Kjy8qzUktPsQozcGiJM57oetkvJBAemJJanZq akFqEUyWiYNTqoHpgNQ5hkvNM3Y8e7Kjd/GZ9/Y/Tz3MnerwcuGk+2n3TF8/PWU2t3VBMC+T 6IfXQpmGRnUiVhrT7kc+X91+dPZxM7bwjxM65y2JUFLceXlS0M8Aq1v9B9dvuVEeqzineFlY zIWqLVlbbVX2KKnyxgjIeAhr2237I2If+qTlcMqdL5Yv9M6891bcpMrS3r40zbrom/aGwK9/ 79RMXThLMm9Z1JTnng9nRb7+VPI5MU7o5JaJhlO2Pp/6++6SjrxvdjVbpz3/PM0qTbTjhYB2 HuNVKym562rt3tKvVqZMV39c1WArnL1lZUH4/ymBszftzs2yCcs9tdXQzVLmN3fs0j1yu6Oe rPmmPG3v9uvPfvoLVCmxFGckGmoxFxUnAgBpP4tyCwMAAA== X-CMS-MailID: 20210126050803epcas1p181f28ec96236552fad1901672aed6f2b X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20210125184007epcas1p39999c1e4325b738e4ff5e42899b8f6b7 References: <000000000000c2865c05b9bcee02@google.com> <20210125183918.GH308988@casper.infradead.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > On Mon, Jan 25, 2021 at 09:33:14AM -0800, syzbot wrote: > > > UBSAN: shift-out-of-bounds in fs/exfat/super.c:471:28 shift exponent > > > 4294967294 is too large for 32-bit type 'int' > > > > This is an integer underflow: > > > > sbi->dentries_per_clu = 1 << > > (sbi->cluster_size_bits - DENTRY_SIZE_BITS); > > > > I think the problem is that there is no validation of sect_per_clus_bits. > > We should check it is at least DENTRY_SIZE_BITS and probably that it's > > less than ... 16? 64? I don't know what legitimate values are in this field, but I would imagine > that 255 is completely unacceptable. > exfat specification describe sect_per_clus_bits field of boot sector could be at most 32 and at least typo ^^16 > 0. And sect_size_bits can also affect this calculation, It also needs validation. > I will fix it. > Thanks!