linux-ext4 - Re: [PATCH] filefrag: avoid temporary buffer overflow

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Message-Id: <DD4F691A-7672-481D-AA3B-4D4B3BAB84F5@dilger.ca>
Date:   Thu, 1 Mar 2018 16:34:30 -0700
From:   Andreas Dilger <adilger@...ger.ca>
To:     Theodore Ts'o <tytso@....edu>
Cc:     linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] filefrag: avoid temporary buffer overflow

On Mar 1, 2018, at 1:09 PM, Andreas Dilger <adilger@...ger.ca> wrote:
> If an unknown flag is present in a FIEMAP extent, it is printed as a
> hex value into a temporary buffer before adding it to the flags.  If
> that unknown flag is over 0xffff then it will overflow the temporary
> buffer.

Correction, any unknown flag over 0xfff would overflow the old buffer size.

> Reported-by: Sarah Liu <wei3.liu@...el.com>
> Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-10335
> Signed-off-by: Andreas Dilger <andreas.dilger@...el.com>
> ---
> misc/filefrag.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/misc/filefrag.c b/misc/filefrag.c
> index 9c57ab9..dc00393 100644
> --- a/misc/filefrag.c
> +++ b/misc/filefrag.c
> @@ -179,7 +179,7 @@ static void print_extent_info(struct fiemap_extent *fm_extent, int cur_ex,
> 	print_flag(&fe_flags, FIEMAP_EXTENT_SHARED, flags, "shared,");
> 	/* print any unknown flags as hex values */
> 	for (mask = 1; fe_flags != 0 && mask != 0; mask <<= 1) {
> -		char hex[6];
> +		char hex[sizeof(mask) * 2 + 4]; /* 2 chars/byte + 0x, + NUL */
> 
> 		if ((fe_flags & mask) == 0)
> 			continue;
> --
> 1.8.0
> 


Cheers, Andreas






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