| Message ID | 20231025202019.5228-1-s.shtylyov@omp.ru (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [f2fs-dev] f2fs: data: fix possible overflow in check_swap_activate() | expand |
Hi Sergey, Thanks for the patch. On 2023/10/26 4:20, Sergey Shtylyov 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. > > 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)) 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;
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
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) + *span = 1 + highest_pblock - lowest_pblock; + else + *span = 0; if (cur_lblock == 0) cur_lblock = 1; /* force Empty message */ sis->max = cur_lblock;
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... 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(-)