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! BR, Jarkko
