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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3997f9a50c1sm3609957f8f.38.2025.03.21.15.46.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Mar 2025 15:46:13 -0700 (PDT) From: David Laight To: linux-kernel@vger.kernel.org Cc: David Laight , Linus Torvalds , Jens Axboe , David Howells , Matthew Wilcox , Andrew Morton , Alexander Viro Subject: [PATCH next 2/3] iov: Use masked user accesses Date: Fri, 21 Mar 2025 22:45:56 +0000 Message-Id: <20250321224557.3847-3-david.laight.linux@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250321224557.3847-1-david.laight.linux@gmail.com> References: <20250321224557.3847-1-david.laight.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Check can_do_masked_user_access() and use mask_user_address() or masked_user_access_begin() to optimise user access checks. Read iov->buf before iov->len to ensure accessing the 'masked' address fails when kernel addresses are converted to ~0ul. Signed-off-by: David Laight --- lib/iov_iter.c | 44 ++++++++++++++++++++++++++++---------------- 1 file changed, 28 insertions(+), 16 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 623ec43e049a..796ef647bff2 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -19,12 +19,15 @@ size_t copy_to_user_iter(void __user *iter_to, size_t progress, { if (should_fail_usercopy()) return len; - if (access_ok(iter_to, len)) { - from += progress; - instrument_copy_to_user(iter_to, from, len); - len = raw_copy_to_user(iter_to, from, len); - } - return len; + + if (can_do_masked_user_access()) + iter_to = mask_user_address(iter_to); + else if (!access_ok(iter_to, len)) + return len; + + from += progress; + instrument_copy_to_user(iter_to, from, len); + return raw_copy_to_user(iter_to, from, len); } static __always_inline @@ -49,12 +52,17 @@ size_t copy_from_user_iter(void __user *iter_from, size_t progress, if (should_fail_usercopy()) return len; - if (access_ok(iter_from, len)) { - to += progress; - instrument_copy_from_user_before(to, iter_from, len); - res = raw_copy_from_user(to, iter_from, len); - instrument_copy_from_user_after(to, iter_from, len, res); - } + + if (can_do_masked_user_access()) + iter_from = mask_user_address(iter_from); + else if (!access_ok(iter_from, len)) + return len; + + to += progress; + instrument_copy_from_user_before(to, iter_from, len); + res = raw_copy_from_user(to, iter_from, len); + instrument_copy_from_user_after(to, iter_from, len, res); + return res; } @@ -1326,15 +1334,17 @@ static __noclone int copy_compat_iovec_from_user(struct iovec *iov, int ret = -EFAULT; u32 i; - if (!user_access_begin(uiov, nr_segs * sizeof(*uiov))) + if (can_do_masked_user_access()) + uiov = masked_user_access_begin(uiov); + else if (!user_access_begin(uiov, nr_segs * sizeof(*uiov))) return -EFAULT; for (i = 0; i < nr_segs; i++) { compat_uptr_t buf; compat_ssize_t len; - unsafe_get_user(len, &uiov[i].iov_len, uaccess_end); unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end); + unsafe_get_user(len, &uiov[i].iov_len, uaccess_end); /* check for compat_size_t not fitting in compat_ssize_t .. */ if (len < 0) { @@ -1356,15 +1366,17 @@ static __noclone int copy_iovec_from_user(struct iovec *iov, { int ret = -EFAULT; - if (!user_access_begin(uiov, nr_segs * sizeof(*uiov))) + if (can_do_masked_user_access()) + uiov = masked_user_access_begin(uiov); + else if (!user_access_begin(uiov, nr_segs * sizeof(*uiov))) return -EFAULT; do { void __user *buf; ssize_t len; - unsafe_get_user(len, &uiov->iov_len, uaccess_end); unsafe_get_user(buf, &uiov->iov_base, uaccess_end); + unsafe_get_user(len, &uiov->iov_len, uaccess_end); /* check for size_t not fitting in ssize_t .. */ if (unlikely(len < 0)) { -- 2.39.5