Messages in this thread | | | Subject | Re: [PATCH] f2fs: data: fix possible overflow in check_swap_activate() | From | Sergey Shtylyov <> | Date | Mon, 11 Dec 2023 00:14:16 +0300 |
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Hello!
Sorry for replying a month later than I should -- I got distracted by the other Svace reports... It took a significant part of the weekend to swap this stuff back in... :-/
On 11/7/23 6:29 PM, Chao Yu wrote: [...] >> In check_swap_activate(), if the *while* loop exits early (0- or 1-page >> long swap file), an overflow happens while calculating the value of the >> span parameter as the lowest_pblock variable ends up being greater than >> the highest_pblock variable. Let's set *span to 0 in this case... > > What do you think of returning -EINVAL for such case? I assume this is a > corner case.
I don't know the code well enough but I got the impression that iff we have a file containing a single page, we'd have one successful call of add_swap_extent(). Am I missing something?
>> Found by Linux Verification Center (linuxtesting.org) with the SVACE static >> analysis tool. >> >> Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru> >> --- >> This patch is against the 'master' branch of Jaegeuk Kim's F2FS repo... >> >> fs/f2fs/data.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >> index 916e317ac925..342cb0d5056d 100644 >> --- a/fs/f2fs/data.c >> +++ b/fs/f2fs/data.c >> @@ -4047,7 +4047,10 @@ static int check_swap_activate(struct swap_info_struct *sis, >> cur_lblock += nr_pblocks; >> } >> ret = nr_extents; >> - *span = 1 + highest_pblock - lowest_pblock; >> + if (lowest_pblock <= highest_pblock) > > if (unlikely(higest_pblock < lowest_pblock))
Well, Greg KH says we shouldn't use unlikely() unless we can prove that it indeed improves things...
> return -EINVAL; > > *span = 1 + highest_pblock - lowest_pblock; > > Thanks, > >> + *span = 1 + highest_pblock - lowest_pblock; >> + else >> + *span = 0; >> if (cur_lblock == 0) >> cur_lblock = 1; /* force Empty message */ >> sis->max = cur_lblock;
MBR, Sergey
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