RE: [PATCH] megaraid driver fix for 2.5.70

From: James Bottomley (James.Bottomley@steeleye.com)
Date: Fri Jun 06 2003 - 08:46:52 EST


On Fri, 2003-06-06 at 09:28, Mukker, Atul wrote:
> Coming back to main issue, declaring complete mailbox would be superfluous
> since driver uses 16 bytes at most. The following patch should fix the panic
>
> mbox = (mbox_t *)raw_mbox;
>
> - memset(mbox, 0, sizeof(*mbox));
> + memset(mbox, 0, 16);
>
> memset((void *)adapter->mega_buffer, 0, MEGA_BUFFER_SIZE);
>

This, I think, is a bad idea. It looks intrinsically wrong to allocate
storage and assign a pointer to it of a type that is longer than the
allocated storage. The initial buffer overrun was due to problems with
this.

I think the correct solution is to define your mailbox like this:

typedef struct {
        /* 0x0 */ u8 cmd;
        /* 0x1 */ u8 cmdid;
        /* 0x2 */ u16 numsectors;
        /* 0x4 */ u32 lba;
        /* 0x8 */ u32 xferaddr;
        /* 0xC */ u8 logdrv;
        /* 0xD */ u8 numsgelements;
        /* 0xE */ u8 resvd;
        /* 0xF */ volatile u8 busy;
} __attribute__ ((packed)) user_mbox_t;

typedef struct {
        user_mbox_t mbox_out
        /* 0x10 */ volatile u8 numstatus;
        /* 0x11 */ volatile u8 status;
        /* 0x12 */ volatile u8 completed[MAX_FIRMWARE_STATUS];
        volatile u8 poll;
        volatile u8 ack;
} __attribute__ ((packed)) mbox_t;

and then re-define the issue_scb..() routines to use user_mbox_t which
is always the correct size.

Thus, you can throw away the raw_mbox and just do

user_mbox_t mbox;
memset(&mbox, 0, sizeof(mbox));

of course, your ->busy references become ->mbox_out.busy.

James

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