On Thu Mar 7, 2024 at 10:01 PM EET, Jarkko Sakkinen wrote: > On Tue Mar 5, 2024 at 2:27 PM EET, Christian Brauner wrote: > > The vfs_getxattr_alloc() interface is a special-purpose in-kernel api > > that does a racy query-size+allocate-buffer+retrieve-data. It is used by > > EVM, IMA, and fscaps to retrieve xattrs. Recently, we've seen issues > > where 9p returned values that amount to allocating about 8000GB worth of > > memory (cf. [1]). That's now fixed in 9p. But vfs_getxattr_alloc() has > > no reason to allow getting xattr values that are larger than > > XATTR_MAX_SIZE as that's the limit we use for setting and getting xattr > > values and nothing currently goes beyond that limit afaict. Let it check > > for that and reject requests that are larger than that. > > > > Link: https://lore.kernel.org/r/ZeXcQmHWcYvfCR93@do-x1extreme [1] > > Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> > > --- > > fs/xattr.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/fs/xattr.c b/fs/xattr.c > > index 09d927603433..a53c930e3018 100644 > > --- a/fs/xattr.c > > +++ b/fs/xattr.c > > @@ -395,6 +395,9 @@ vfs_getxattr_alloc(struct mnt_idmap *idmap, struct dentry *dentry, > > if (error < 0) > > return error; > > > > + if (error > XATTR_SIZE_MAX) > > + return -E2BIG; > > + > > if (!value || (error > xattr_size)) { > > value = krealloc(*xattr_value, error + 1, flags); > > if (!value) > > I wonder if this should even categorized as a bug fix and get > backported. Good catch! Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> BR, Jarkko
