From: lianzhi chang <changlianzhi@xxxxxxxxxxxxx> [ Upstream commit 5cdc4a6950a883594e9640b1decb3fcf6222a594 ] 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. Link: https://lore.kernel.org/r/20210114075741.30448-1-changlianzhi@xxxxxxxxxxxxx Signed-off-by: lianzhi chang <changlianzhi@xxxxxxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 4aba4878ed967..8bb001c7927f0 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 session_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); + session_offset = (loff_t)sbi->s_session << sb->s_blocksize_bits; + sector += session_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 - session_offset == VSD_FIRST_SECTOR_OFFSET) return -1; else return 0; -- 2.27.0
