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101 lines
3.2 KiB
Diff
101 lines
3.2 KiB
Diff
Patch from:
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https://gitlab.com/qemu-project/qemu/-/commit/a4ad4a9d98f7fbde806f07da21e69f39e134cdf1
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From a4ad4a9d98f7fbde806f07da21e69f39e134cdf1 Mon Sep 17 00:00:00 2001
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From: Richard Henderson <richard.henderson@linaro.org>
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Date: Fri, 16 Aug 2024 07:13:31 +1000
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Subject: [PATCH] linux-user: Handle short reads in mmap_h_gt_g
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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In particular, if an image has a large bss, we can hit
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EOF before reading all host_len bytes of the mapping.
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Create a helper, mmap_pread to handle the job for both
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the larger block in mmap_h_gt_g itself, as well as the
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smaller block in mmap_frag.
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Cc: qemu-stable@nongnu.org
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Fixes: eb5027ac618 ("linux-user: Split out mmap_h_gt_g")
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2504
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Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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Message-Id: <20240820050848.165253-2-richard.henderson@linaro.org>
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Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
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---
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linux-user/mmap.c | 44 ++++++++++++++++++++++++++++++++++++++------
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1 file changed, 38 insertions(+), 6 deletions(-)
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diff --git a/linux-user/mmap.c b/linux-user/mmap.c
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index 6418e811f6..e4bf5d5f39 100644
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--- a/linux-user/mmap.c
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+++ b/linux-user/mmap.c
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@@ -283,6 +283,40 @@ static int do_munmap(void *addr, size_t len)
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return munmap(addr, len);
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}
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+/*
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+ * Perform a pread on behalf of target_mmap. We can reach EOF, we can be
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+ * interrupted by signals, and in general there's no good error return path.
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+ * If @zero, zero the rest of the block at EOF.
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+ * Return true on success.
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+ */
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+static bool mmap_pread(int fd, void *p, size_t len, off_t offset, bool zero)
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+{
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+ while (1) {
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+ ssize_t r = pread(fd, p, len, offset);
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+
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+ if (likely(r == len)) {
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+ /* Complete */
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+ return true;
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+ }
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+ if (r == 0) {
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+ /* EOF */
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+ if (zero) {
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+ memset(p, 0, len);
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+ }
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+ return true;
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+ }
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+ if (r > 0) {
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+ /* Short read */
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+ p += r;
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+ len -= r;
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+ offset += r;
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+ } else if (errno != EINTR) {
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+ /* Error */
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+ return false;
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+ }
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+ }
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+}
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+
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/*
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* Map an incomplete host page.
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*
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@@ -357,10 +391,9 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last,
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/* Read or zero the new guest pages. */
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if (flags & MAP_ANONYMOUS) {
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memset(g2h_untagged(start), 0, last - start + 1);
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- } else {
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- if (pread(fd, g2h_untagged(start), last - start + 1, offset) == -1) {
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- return false;
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- }
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+ } else if (!mmap_pread(fd, g2h_untagged(start), last - start + 1,
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+ offset, true)) {
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+ return false;
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}
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/* Put final protection */
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@@ -853,8 +886,7 @@ static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
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}
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if (misaligned_offset) {
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- /* TODO: The read could be short. */
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- if (pread(fd, p, host_len, offset + real_start - start) != host_len) {
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+ if (!mmap_pread(fd, p, host_len, offset + real_start - start, false)) {
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do_munmap(p, host_len);
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return -1;
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}
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--
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2.46.0
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