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SubjectRe: [PATCH v4] f2fs: fix potential .flags overflow on 32bit architecture
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On 2020/3/23 10:57, Joe Perches wrote:
> On Mon, 2020-03-23 at 10:41 +0800, Chao Yu wrote:
>> f2fs_inode_info.flags is unsigned long variable, it has 32 bits
>> in 32bit architecture, since we introduced FI_MMAP_FILE flag
>> when we support data compression, we may access memory cross
>> the border of .flags field, corrupting .i_sem field, result in
>> below deadlock.
> []
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> []
>> @@ -682,6 +682,47 @@ enum {
> []
>> +/* used for f2fs_inode_info->flags */
>> +enum {
> []
>> + FI_MAX, /* max flag, never be used */
>> +};
>> +
>> +/* f2fs_inode_info.flags array size */
>> +#define FI_ARRAY_SIZE (BITS_TO_LONGS(FI_MAX))
>
> Perhaps FI_ARRAY_SIZE isn't necessary.
>
>> +
>> struct f2fs_inode_info {
>> struct inode vfs_inode; /* serve a vfs inode */
>> unsigned long i_flags; /* keep an inode flags for ioctl */
>> @@ -694,7 +735,7 @@ struct f2fs_inode_info {
>> umode_t i_acl_mode; /* keep file acl mode temporarily */
>>
>> /* Use below internally in f2fs*/
>> - unsigned long flags; /* use to pass per-file flags */
>> + unsigned long flags[FI_ARRAY_SIZE]; /* use to pass per-file flags */
>
> and BITS_TO_LONGS should be used here.
>
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> []
>> @@ -362,7 +363,8 @@ static int do_read_inode(struct inode *inode)
>> fi->i_flags = le32_to_cpu(ri->i_flags);
>> if (S_ISREG(inode->i_mode))
>> fi->i_flags &= ~F2FS_PROJINHERIT_FL;
>> - fi->flags = 0;
>> + for (i = 0; i < FI_ARRAY_SIZE; i++)
>> + fi->flags[i] = 0;
>
> And this could become
>
> bitmap_zero(fi->flags, BITS_TO_LONG(FI_MAX));
>
> Is FI_ARRAY_SIZE used anywhere else?

Updated in v5, thanks.

Thanks,

>
> .
>

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