Hi, On Thu, Nov 12, 2020 at 10:30:04AM -0800, Darrick J. Wong wrote: > On Thu, Nov 12, 2020 at 09:53:53AM -0600, Eric Sandeen wrote: > > On 11/12/20 12:30 AM, Gao Xiang wrote: > > > Currently, commit e9e2eae89ddb dropped a (int) decoration from > > > XFS_LITINO(mp), and since sizeof() expression is also involved, > > > the result of XFS_LITINO(mp) is simply as the size_t type > > > (commonly unsigned long). > > > > Thanks for finding this! Let me think through it a little. > > > > > Considering the expression in xfs_attr_shortform_bytesfit(): > > > offset = (XFS_LITINO(mp) - bytes) >> 3; > > > let "bytes" be (int)340, and > > > "XFS_LITINO(mp)" be (unsigned long)336. > > > > > > on 64-bit platform, the expression is > > > offset = ((unsigned long)336 - (int)340) >> 8 = > > > > This should be >> 3, right. > > > > > (int)(0xfffffffffffffffcUL >> 3) = -1 > > > > > > but on 32-bit platform, the expression is > > > offset = ((unsigned long)336 - (int)340) >> 8 = > > > > and >> 3 here as well. > > > > > (int)(0xfffffffcUL >> 3) = 0x1fffffff > > > instead. > > > > Ok. But wow, that magical cast to (int) in XFS_LITINO isn't at > > all clear to me. > > > > XFS_LITINO() indicates a /size/ - fixing this problem by making it a > > signed value feels very strange, but I'm not sure what would be better, > > yet. > > TBH I think this needs to be cleaned up -- what is "LITINO", anyway? > > I'm pretty sure it's the size of the literal area, aka everything after > the inode core, where the forks live? > > And, uh, can these things get turned into static inline helpers instead > of weird macros? Separate patches, obviously. Thanks, I've addressed all comments in these two reviews in v2: https://lore.kernel.org/r/20201113015044.844213-1-hsiangkao@xxxxxxxxxx As for LITINO itself, btw, what would be the suggested name for this? I'm not good at naming, and will seek time working on cleaning up this. > > > > > > Therefore, one result is > > > "ASSERT(new_size <= XFS_IFORK_SIZE(ip, whichfork));" > > > assertion failure in xfs_idata_realloc(). > > > > > > , which can be triggered with the following commands: > > > touch a; > > > setfattr -n user.0 -v "`seq 0 80`" a; > > > setfattr -n user.1 -v "`seq 0 80`" a > > > on 32-bit platform. > > > > Can you please write an xfstest for this? :) > > Seconded. Will seek time on this later as well. > > If this is the fix for the corruption report that dgilmore reported on > IRC, this should credit him as the reporter and/or tester. Especially > because I thought this was just a "oh I found this via code review" > until someone else pointed out that this was actually a fix for > something that a user hit in the field. > > The difference is that we're headed towards -rc4 and I'm much more > willing to hold up posting the xfs-5.11-merge branch to get in fixes for > user-reported problems. Yeah, sorry for ignoring this original bugreport, since I thought the original bugzilla couldn't open publicly. https://bugzilla.redhat.com/show_bug.cgi?id=1894177 It would be better to get a "Tested-by:" tag to check the original case for v2. :) > > > > Fix it by restoring (int) decorator to XFS_LITINO(mp) since > > > int type for XFS_LITINO(mp) is safe and all pre-exist signed > > > calculations are correct. > > > > > > Fixes: e9e2eae89ddb ("xfs: only check the superblock version for dinode size calculation") > > > Cc: <stable@xxxxxxxxxxxxxxx> # 5.7+ > > > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx> > > > --- > > > I'm not sure this is the preferred way or just simply fix > > > xfs_attr_shortform_bytesfit() since I don't look into the > > > rest of XFS_LITINO(mp) users. Add (int) to XFS_LITINO(mp) > > > will avoid all potential regression at least. > > > > > > fs/xfs/libxfs/xfs_format.h | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h > > > index dd764da08f6f..f58f0a44c024 100644 > > > --- a/fs/xfs/libxfs/xfs_format.h > > > +++ b/fs/xfs/libxfs/xfs_format.h > > > @@ -1061,7 +1061,7 @@ enum xfs_dinode_fmt { > > > sizeof(struct xfs_dinode) : \ > > > offsetof(struct xfs_dinode, di_crc))> #define XFS_LITINO(mp) \ > > > - ((mp)->m_sb.sb_inodesize - XFS_DINODE_SIZE(&(mp)->m_sb)) > > > + ((int)((mp)->m_sb.sb_inodesize - XFS_DINODE_SIZE(&(mp)->m_sb))) > > > > If we do keep the (int) cast here we at least need a comment explaining why > > it cannot be removed, unless there is a better way to solve the problem. > > It's still weird, because "size of literal inode area" isn't a signed > quantity because you can't have a negative size. I'm fine with either way, since my starting point was to address the regression of e9e2eae89ddb as I mentioned on IRC. And it can also be simply fixed directly. Thanks, Gao Xiang > > > I wonder if explicitly making XFS_LITINO() cast to a size_t would be > > best, and then in xfs_attr_shortform_bytesfit() we just quickly reject > > the query if the bytes are larger than the literal area: > > > > diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c > > index bb128db..5588c2e 100644 > > --- a/fs/xfs/libxfs/xfs_attr_leaf.c > > +++ b/fs/xfs/libxfs/xfs_attr_leaf.c > > @@ -535,6 +535,10 @@ STATIC void xfs_attr3_leaf_moveents(struct xfs_da_args *args, > > int maxforkoff; > > int offset; > > > > + /* Is there no chance we can fit? */ > > + if (bytes > XFS_LITINO(mp)) > > + return 0; > > + > > /* rounded down */ > > offset = (XFS_LITINO(mp) - bytes) >> 3; > > So if LITINO is 336 and the caller asked for 350 bytes, offset will be > negative here. However, offset is the proposed forkoff, right? It > doesn't make any sense to have a negative forkoff, so I think Eric's > (bytes > LITINO) suggestion above is correct. > > This patch was hard to review because the comment for > xfs_attr_shortform_bytesfit mentions "...the requested number of > additional bytes", but the bytes parameter represents the total number > of attr fork bytes we want, not a delta over what we have right now. > Can someone please fix that comment too? > > --D > > > > > or, maybe simply: > > > > - offset = (XFS_LITINO(mp) - bytes) >> 3; > > + offset = (int)(XFS_LITINO(mp) - bytes) >> 3; > > > > to be sure that the arithmetic doesn't get promoted to unsigned before the shift? > > > > or maybe others have better ideas. > > > > -Eric > > > > > > > /* > > > * Inode data & attribute fork sizes, per inode. > > > >
