Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding

[Jens Remus <jremus@linux.ibm.com>]

On 28.10.2024 22:47, Josh Poimboeuf wrote:
...
> diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
...
> +static int find_fde(struct sframe_section *sec, unsigned long ip,
> +		    struct sframe_fde *fde)
> +{
> +	struct sframe_fde __user *first, *last, *found = NULL;
> +	u32 ip_off, func_off_low = 0, func_off_high = -1;
> +
> +	ip_off = ip - sec->sframe_addr;
> +
> +	first = (void __user *)sec->fdes_addr;
> +	last = first + sec->fdes_nr;

Could it be that this needs to be:

	last = first + sec->fdes_nr - 1;

> +	while (first <= last) {
> +		struct sframe_fde __user *mid;
> +		u32 func_off;
> +
> +		mid = first + ((last - first) / 2);
> +
> +		if (get_user(func_off, (s32 __user *)mid))
> +			return -EFAULT;
> +
> +		if (ip_off >= func_off) {
> +			/* validate sort order */
> +			if (func_off < func_off_low)
> +				return -EINVAL;

Otherwise I run into this when the IP is within the function whose FDE 
is the last one in the .sframe section:

find_fde: IP=0x000000000110fbcc: ERROR: func_off < func_off_low 
(func_off=196608, func_off_low=4294224904)

110fbcc dump_sframe+0x2ec (/opt/binutils-sframe2/bin/objdump)

func idx [2275]: pc = 0x110f8e0, size = 3310 bytes <dump_sframe>
STARTPC         CFA       FP        RA           INFO
000000000110f8e0  sp+160    u         u            (1*1B)
000000000110f8e6  sp+160    c-72      c-48         (3*1B)
000000000110f8f6  sp+632    c-72      c-48         (3*1B)
000000000110fa82  sp+160    u         u            (1*1B)
000000000110fa88  sp+632    c-72      c-48         (3*1B)
0000000001110486  sp+160    u         u            (1*1B)
000000000111048c  sp+632    c-72      c-48         (3*1B)
0000000001110574  sp+160    u         u            (1*1B)
000000000111057a  sp+632    c-72      c-48         (3*1B)

> +
> +			func_off_low = func_off;
> +
> +			found = mid;
> +			first = mid + 1;
> +		} else {
> +			/* validate sort order */
> +			if (func_off > func_off_high)
> +				return -EINVAL;
> +
> +			func_off_high = func_off;
> +
> +			last = mid - 1;
> +		}
> +	}
> +
> +	if (!found)
> +		return -EINVAL;
> +
> +	if (copy_from_user(fde, found, sizeof(*fde)))
> +		return -EFAULT;
> +
> +	/* check for gaps */
> +	if (ip_off < fde->start_addr || ip_off >= fde->start_addr + fde->size)
> +		return -EINVAL;
> +
> +	return 0;
> +}

Thanks and regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303) and z/VSE Support
+49-7031-16-1128 Office
jremus@de.ibm.com

IBM

IBM Deutschland Research & Development GmbH; Vorsitzender des 
Aufsichtsrats: Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der 
Gesellschaft: Böblingen; Registergericht: Amtsgericht Stuttgart, HRB 243294
IBM Data Privacy Statement: https://www.ibm.com/privacy/