3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
commit a13f085d111e90469faf2d9965eb39b11c114d7e upstream.
This fixes the following issues:
- When a buffer size is supplied to reiserfs_listxattr() such that each individual name fits, but the concatenation of all names doesn't fit, reiserfs_listxattr() overflows the supplied buffer. This leads to a kernel heap overflow (verified using KASAN) followed by an out-of-bounds usercopy and is therefore a security bug.
- When a buffer size is supplied to reiserfs_listxattr() such that a name doesn't fit, -ERANGE should be returned. But reiserfs instead just truncates the list of names; I have verified that if the only xattr on a file has a longer name than the supplied buffer length, listxattr() incorrectly returns zero.
With my patch applied, -ERANGE is returned in both cases and the memory corruption doesn't happen anymore.
Credit for making me clean this code up a bit goes to Al Viro, who pointed out that the ->actor calling convention is suboptimal and should be changed.
Link: http://lkml.kernel.org/r/20180802151539.5373-1-jannh@google.com Fixes: 48b32a3553a5 ("reiserfs: use generic xattr handlers") Signed-off-by: Jann Horn jannh@google.com Acked-by: Jeff Mahoney jeffm@suse.com Cc: Eric Biggers ebiggers@google.com Cc: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [bwh: Backported to 3.16: - The xattr handler's list operation does the copy, so also update the buffer size we pass to it - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/fs/reiserfs/xattr.c +++ b/fs/reiserfs/xattr.c @@ -822,10 +822,12 @@ static int listxattr_filler(void *buf, c return 0; if (b->buf) { size = handler->list(b->dentry, b->buf + b->pos, - b->size, name, namelen, + b->size - b->pos, name, namelen, handler->flags); - if (size > b->size) + if (b->pos + size > b->size) { + b->pos = -ERANGE; return -ERANGE; + } } else { size = handler->list(b->dentry, NULL, 0, name, namelen, handler->flags);