NULL pointer deref crash on barebox 2020.08.0

[Ahmad Fatoum]

Hello Giorgio,

On 8/20/20 2:18 PM, Giorgio Dal Molin wrote:
> Hi,
> 
> I've tried the current barebox v2020.08.0 on my imx7d module and it crashes
> while executing the command:
> 
> imx7d: / cp /mnt/boot/kernel.img /dev/mmc1.fw_update
> unable to handle NULL pointer dereference at address 0x00000000
> pc : [<ffe6c2dc>]    lr : [<ffe6c2c0>]
> sp : fffefcd0  ip : fffefcd0  fp : c00f8850
> r10: ffe981ef  r9 : 00000000  r8 : ffe981ef
> r7 : ffe98dcb  r6 : ffea60a8  r5 : ffe98dbd  r4 : c00ef1e8
> r3 : 00000000  r2 : bfefb8e0  r1 : ffe98dbd  r0 : 00028888
> Flags: nZCv  IRQs off  FIQs off  Mode SVC_32
> 
> no stack data available
> 
> 
> I could track the problem down to a call to list_del(&inode->i_sb_list); in
> fs/fs.c:iput(struct inode *inode):
> 
> void iput(struct inode *inode)
> {
> 	if (!inode)
> 		return;
> 
> 	inode->i_count--;
> 
> 	if (!inode->i_count) {
> 		list_del(&inode->i_sb_list);        <== this call segfaults
> 		destroy_inode(inode);
> 	}
> }
> 
> I've checked that the struct list_head inode->i_sb_list has its .prev pointer NULL
> and that's the immediate reason why I get a segfault (at WRITE_ONCE(prev->next, next)
> in __list_del(prev, next); what I don't know is whether a NULL .prev is OK and the error
> is a missing test in __list_del() or if a NULL .prev is already wrong.

What kind of file system is mounted at /mnt/boot?

> 
> giorgio
> 
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> 

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