Messages in this thread Patch in this message | | | From | sel4@tilde ... | Subject | [PATCH] fortify: strnlen: Call fortify_panic() only if the number of bytes read is greater than maxlen | Date | Mon, 24 Jul 2023 22:48:57 +0000 |
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From: Brandon Luo <sel4@tilde.club>
If the number of bytes read is p_size and p_size is less than maxlen, fortify_panic() will be called incorrectly. Only panic if the number of bytes read is greater than the minimum of p_size and maxlen since that is the argument to __real_strnlen().
Reported-by: syzbot+98d3ceb7e01269e7bf4f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000d8352e0600c0c804@google.com/
Reported-by: syzbot+155274e882dcbf9885df@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000de4c2c0600c02b28@google.com/
Signed-off-by: Brandon Luo <sel4@tilde.club> --- include/linux/fortify-string.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index da51a83b2829..cde637f735fe 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -176,8 +176,9 @@ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size } /* Do not check characters beyond the end of p. */ - ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size); - if (p_size <= ret && maxlen != ret) + maxlen = (maxlen < p_size) ? maxlen : p_size; + ret = __real_strnlen(p, maxlen); + if (maxlen < ret) fortify_panic(__func__); return ret; } -- 2.41.0
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