lkml.org 
[lkml]   [2021]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] udf: fix the problem that the disc content is not displayed
On Thu 14-01-21 15:57:41, lianzhi chang wrote:
> When the capacity of the disc is too large (assuming the 4.7G
> specification), the disc (UDF file system) will be burned
> multiple times in the windows (Multisession Usage). When the
> remaining capacity of the CD is less than 300M (estimated
> value, for reference only), open the CD in the Linux system,
> the content of the CD is displayed as blank (the kernel will
> say "No VRS found"). Windows can display the contents of the
> CD normally.
> Through analysis, in the "fs/udf/super.c": udf_check_vsd
> function, the actual value of VSD_MAX_SECTOR_OFFSET may
> be much larger than 0x800000. According to the current code
> logic, it is found that the type of sbi->s_session is "__s32",
> when the remaining capacity of the disc is less than 300M
> (take a set of test values: sector=3154903040,
> sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
> calculation result of "sbi->s_session << sb->s_blocksize_bits"
> will overflow. Therefore, it is necessary to convert the
> type of s_session to "loff_t" (when udf_check_vsd starts,
> assign a value to _sector, which is also converted in this
> way), so that the result will not overflow, and then the
> content of the disc can be displayed normally.
>
> Signed-off-by: lianzhi chang <changlianzhi@uniontech.com>
> ---
> fs/udf/super.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/udf/super.c b/fs/udf/super.c
> index 5bef3a68395d..f2ff98f393fb 100644
> --- a/fs/udf/super.c
> +++ b/fs/udf/super.c
> @@ -705,6 +705,7 @@ static int udf_check_vsd(struct super_block *sb)
> struct buffer_head *bh = NULL;
> int nsr = 0;
> struct udf_sb_info *sbi;
> + loff_t sector_offset;
>
> sbi = UDF_SB(sb);
> if (sb->s_blocksize < sizeof(struct volStructDesc))
> @@ -712,7 +713,8 @@ static int udf_check_vsd(struct super_block *sb)
> else
> sectorsize = sb->s_blocksize;
>
> - sector += (((loff_t)sbi->s_session) << sb->s_blocksize_bits);
> + sector_offset = (loff_t)sbi->s_session << sb->s_blocksize_bits);

There's imbalanced parentheses here, I'll fix it up on commit. Otherwise
the fix looks good to me. Thanks!

Honza

> + sector += sector_offset;
>
> udf_debug("Starting at sector %u (%lu byte sectors)\n",
> (unsigned int)(sector >> sb->s_blocksize_bits),
> @@ -757,8 +759,7 @@ static int udf_check_vsd(struct super_block *sb)
>
> if (nsr > 0)
> return 1;
> - else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) ==
> - VSD_FIRST_SECTOR_OFFSET)
> + else if (!bh && sector - sector_offset == VSD_FIRST_SECTOR_OFFSET)
> return -1;
> else
> return 0;
> --
> 2.20.1
>
>
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR

\
 
 \ /
  Last update: 2021-01-14 11:43    [W:0.071 / U:0.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site