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[PULL,1/2] chardev/char-mux: shift unsigned long to avoid 32-bit overflow

Message ID 20241202122709.100177-2-marcandre.lureau@redhat.com (mailing list archive)
State New
Headers show
Series [PULL,1/2] chardev/char-mux: shift unsigned long to avoid 32-bit overflow | expand

Commit Message

Marc-André Lureau Dec. 2, 2024, 12:27 p.m. UTC 
From: Roman Penyaev <r.peniaev@gmail.com>

Allthough the size of MAX_MUX is equal to 4 and likely will never
change, this patch changes type of constant to unsigned long to
be on the safe side.

Also add a static compile check that MAX_MUX never bigger than
`sizeof(d->mux_bitset) * BITS_PER_BYTE`.

Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>
Reviewed-by: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
Cc: qemu-devel@nongnu.org
Message-ID: <20241129103239.464061-2-r.peniaev@gmail.com>
---
 chardev/char-mux.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
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Patch

diff --git a/chardev/char-mux.c b/chardev/char-mux.c
index bda5c45e60..9d67b8bd9a 100644
--- a/chardev/char-mux.c
+++ b/chardev/char-mux.c
@@ -316,6 +316,8 @@  bool mux_chr_attach_frontend(MuxChardev *d, CharBackend *b,
 {
     unsigned int bit;
 
+    QEMU_BUILD_BUG_ON(MAX_MUX > (sizeof(d->mux_bitset) * BITS_PER_BYTE));
+
     bit = find_next_zero_bit(&d->mux_bitset, MAX_MUX, 0);
     if (bit >= MAX_MUX) {
         error_setg(errp,
@@ -325,7 +327,7 @@  bool mux_chr_attach_frontend(MuxChardev *d, CharBackend *b,
         return false;
     }
 
-    d->mux_bitset |= (1 << bit);
+    d->mux_bitset |= (1ul << bit);
     d->backends[bit] = b;
     *tag = bit;
 
@@ -341,7 +343,7 @@  bool mux_chr_detach_frontend(MuxChardev *d, unsigned int tag)
         return false;
     }
 
-    d->mux_bitset &= ~(1 << bit);
+    d->mux_bitset &= ~(1ul << bit);
     d->backends[bit] = NULL;
 
     return true;