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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id c25sm5919465pfo.101.2021.03.12.12.56.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Mar 2021 12:56:08 -0800 (PST) From: Kees Cook To: Andrew Morton Cc: Kees Cook , Greg Kroah-Hartman , Michal Hocko , Alexey Dobriyan , Lee Duncan , Chris Leech , Adam Nichols , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] seq_file: Unconditionally use vmalloc for buffer Date: Fri, 12 Mar 2021 12:55:58 -0800 Message-Id: <20210312205558.2947488-1-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Patch-Hashes: v=1; h=sha256; g=6e23cb09e9c77602ae36025771732e214a07d5d1; i=wnTs9CQ9b8oyAQUYWk1TWb6rr60OLTnvw/rrLAiBrmk=; m=mNgWWeM/mV0t2QLIflkURb7sIrkmH0bDqAx9/NsC4HI=; p=mfyYitSAa6+tmp4ZfMy/uMq8hKV0urLrdhp8kEobIBA= X-Patch-Sig: m=pgp; i=keescook@chromium.org; s=0x0x8972F4DFDC6DC026; b=iQIzBAABCgAdFiEEpcP2jyKd1g9yPm4TiXL039xtwCYFAmBL1V0ACgkQiXL039xtwCa3LQ/6Amd tpDEYqTBiE/cyKH5oUqsQxoRBQ19QCQ9ALOD4dXuoBkkGN2Z8c4FJjnPlpgEDPXleFKrWyxGVvQYs gzJxQAsLJ5cG0YYTFGMHHDTrWCNNCqi9+PpSZP8vZ7+HtwsHJIVWrZEGrkYLRIVVrY8sFTWpcKghS YGBi7qPuHqBiz0axrxoqgaX8KKG6wCDpgJn2yPZkwPFvv0gAKRPNdBRbgCk29gs/nc8/1/cPcXZuN fmd1JOG+7QeCK2EZ/0c2WkcYi1/tGVtJuFOeSGqmaJ+te9giO8ttPFZKSf68zxMsffb71+beLFXbx L2mplD8GK/yZZ3rDf7fl36bcIVF1EfzishGjcJEk4qMz+7WfyHCb7cLl74fcsWiv5NVjdQD8UHgdE rvgvzwZ6vo7XEipizdLTILPj7pdW+51I2RvZOreYuQxN3PY0HW4uTVb7RX/FKm4iE/E5birDDza4m Q+HGdnqsqXnni58jFh9EUwGzVeMpksHjIkPrMsy50opl3TAp1149pFv5IbpJ98FKhHpmeD9MqPbG+ EQU+zzxfuD7Tdg0Rq/LeN7/OWQdrdFh4wtU7+O1sbW/LLVyCd0tJEVGhF0FUWKTDLr+PzMLWyA16z dggneBkRh7rz6SCkRsaIXJYYYesvxRwBGxbt1E4u4BGQkdQimA5Y8fQsXpK2tkjc= Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The sysfs interface to seq_file continues to be rather fragile, as seen with some recent exploits[1]. Move the seq_file buffer to the vmap area (while retaining the accounting flag), since it has guard pages that will catch and stop linear overflows. This seems justified given that seq_file already uses kvmalloc(), that allocations are normally short lived, and that they are not normally performance critical. [1] https://blog.grimm-co.com/2021/03/new-old-bugs-in-linux-kernel.html Signed-off-by: Kees Cook --- fs/seq_file.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index cb11a34fb871..ad78577d4c2c 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -32,7 +32,7 @@ static void seq_set_overflow(struct seq_file *m) static void *seq_buf_alloc(unsigned long size) { - return kvmalloc(size, GFP_KERNEL_ACCOUNT); + return __vmalloc(size, GFP_KERNEL_ACCOUNT); } /** @@ -130,7 +130,7 @@ static int traverse(struct seq_file *m, loff_t offset) Eoverflow: m->op->stop(m, p); - kvfree(m->buf); + vfree(m->buf); m->count = 0; m->buf = seq_buf_alloc(m->size <<= 1); return !m->buf ? -ENOMEM : -EAGAIN; @@ -237,7 +237,7 @@ ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter) goto Fill; // need a bigger buffer m->op->stop(m, p); - kvfree(m->buf); + vfree(m->buf); m->count = 0; m->buf = seq_buf_alloc(m->size <<= 1); if (!m->buf) @@ -349,7 +349,7 @@ EXPORT_SYMBOL(seq_lseek); int seq_release(struct inode *inode, struct file *file) { struct seq_file *m = file->private_data; - kvfree(m->buf); + vfree(m->buf); kmem_cache_free(seq_file_cache, m); return 0; } @@ -585,7 +585,7 @@ int single_open_size(struct file *file, int (*show)(struct seq_file *, void *), return -ENOMEM; ret = single_open(file, show, data); if (ret) { - kvfree(buf); + vfree(buf); return ret; } ((struct seq_file *)file->private_data)->buf = buf; -- 2.25.1