48 lines
1.7 KiB
Diff
48 lines
1.7 KiB
Diff
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From 3eb4b5375f7ffca0e21fac479dfa688cae936641 Mon Sep 17 00:00:00 2001
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From: Patrick Steinhardt <ps@pks.im>
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Date: Tue, 29 May 2018 13:20:00 +0200
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Subject: [PATCH 62/65] procio: fix potential out-of-bounds access when write
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fails
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When writing to procfs via `proc_write` fails, we try to chunk the
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buffer into smaller pieces to work around that issue. When searching for
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the next location to split the buffer, though, we can underflow the
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buffer in case the current offset is smaller than `LINELEN`. Fix the
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issue by passing `cookie->offset` instead of `LINELEN` into `memrchr` in
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case `cookie->offset` is smaller than `LINELEN`.
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This bug can be triggered on musl-based systems, e.g. by executing
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$ sysctl kernel.printk_ratelimit=1000000000000000
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As the value is out-of-range, `write` will return an error and set
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`errno` to `EINVAL`. As we're only trying to write a smallish buffer
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with a length smaller than `LINELEN` and as the buffer does not contain
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any newlines, the call
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token = (char*)memrchr(cookie->buf+offset, '\n', LINELEN);
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will underflow the buffer and crash the program.
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Signed-off-by: Patrick Steinhardt <ps@pks.im>
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---
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procio.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/procio.c b/procio.c
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index 2813cd5..f3258ff 100644
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--- a/procio.c
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+++ b/procio.c
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@@ -251,7 +251,7 @@ ssize_t proc_write(void *c, const char *buf, size_t count)
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if (cookie->offset > LINELEN)
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token = (char*)memrchr(cookie->buf+offset, cookie->delim, LINELEN);
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else
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- token = (char*)memrchr(cookie->buf+offset, '\n', LINELEN);
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+ token = (char*)memrchr(cookie->buf+offset, '\n', cookie->offset);
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if (token)
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*token = '\n';
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else {
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--
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2.6.4.windows.1
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