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Re: [XEN PATCH v3 1/3] libxl: Fix nul-termination of the return value of libxl_xen_console_read_line()
- To: Javi Merino <javi.merino@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 3 Sep 2024 08:14:42 +0200
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- Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Edwin Török <edwin.torok@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 03 Sep 2024 06:14:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02.09.2024 18:38, Javi Merino wrote:
> When built with ASAN, "xl dmesg" crashes in the "printf("%s", line)"
> call in main_dmesg(). ASAN reports a heap buffer overflow: an
> off-by-one access to cr->buffer.
>
> The readconsole sysctl copies up to count characters into the buffer,
> but it does not add a null character at the end. Despite the
> documentation of libxl_xen_console_read_line(), line_r is not
> nul-terminated if 16384 characters were copied to the buffer.
>
> Fix this by asking xc_readconsolering() to fill the buffer up to size
> - 1. As the number of characters in the buffer is only needed in
> libxl_xen_console_read_line(), make it a local variable there instead
> of part of the libxl__xen_console_reader struct.
>
> Fixes: 4024bae739cc ("xl: Add subcommand 'xl dmesg'")
> Reported-by: Edwin Török <edwin.torok@xxxxxxxxx>
> Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> Signed-off-by: Javi Merino <javi.merino@xxxxxxxxx>
Please keep tags in chronological order. I almost overlooked the R-b,
which makes this eligible for committing.
Jan
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