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Tue, 17 Mar 2026 14:40:07 -0700 (PDT) Received: from [192.168.0.108] ([2a02:8071:5392:3220::bcad]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b51899622sm2479963f8f.28.2026.03.17.14.40.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Mar 2026 14:40:07 -0700 (PDT) From: Marc Buerg Date: Tue, 17 Mar 2026 22:39:32 +0100 Subject: [PATCH v2] sysctl: fix check against uninitialized variable in proc_do_large_bitmap Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260317-fix-uninitialized-variable-in-proc_do_large_bitmap-v2-1-6dfb1aefa287@googlemail.com> X-B4-Tracking: v=1; b=H4sIABPKuWkC/6WOQQ6CMBBFr2K6dgwtwsKV9zCEDO1QJiktabFRC Xe3cgWX7+fn/b+JRJEpidtpE5EyJw6+gDqfhJ7QWwI2hYWqVFvVUsHIL3h69rwyOv6QgYyRcXC l6WGJQfcm9A6jpX7gdcYF6kq3NF5RS92IIl4iFcsx+ugKT5zWEN/Hhyx/6V9zWYKEukGjjDE4K nm3IVhHM7K76DCLbt/3L+tX4WP5AAAA X-Change-ID: 20260312-fix-uninitialized-variable-in-proc_do_large_bitmap-30c6ef4ac1c5 To: Kees Cook , Joel Granados , "David S. Miller" , Octavian Purdila , WANG Cong Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Elias Oezcan , Peter Seiderer , Marc Buerg X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1773783606; l=1689; i=buermarc@googlemail.com; s=20260312; h=from:subject:message-id; bh=9239N7F1ux6YHvgN4osMP3w6IaeFva0SE8JuYoWDSvo=; b=6QGig6XTTBH1VJmGj0uuZu+dkyo6IuuK2rsSLZyknaYiRGucmEC4+VWOaHZBn/gwD05EOHYkq yIAI1yuULTyCjSTCjAASHNx/qFfrUb0rxfY1Y5JzARcjyB20IR/STe6 X-Developer-Key: i=buermarc@googlemail.com; a=ed25519; pk=kBZIEGh9yNUzqCz87kygF7XqwPxTWvwm4+HUrOuckyM= proc_do_large_bitmap() does not initialize variable c, which is expected to be set to a trailing character by proc_get_long(). However, proc_get_long() only sets c when the input buffer contains a trailing character after the parsed value. If c is not initialized it may happen to contain a '-'. If this is the case proc_do_large_bitmap() expects to be able to parse a second part of the input buffer. If there is no second part an unjustified -EINVAL will be returned. Add check that left is non-zero before checking c, as proc_get_long() ensures that the passed left is non-zero, if a trailing character exists. Reviewed-by: Peter Seiderer --- Fixes: 9f977fb7ae9d ("sysctl: add proc_do_large_bitmap") Signed-off-by: Marc Buerg --- Changes in v2: - Drop initialization of c to 0 - Include checking that left is non-zero before checking against c - Link to v1: https://lore.kernel.org/r/20260312-fix-uninitialized-variable= -in-proc_do_large_bitmap-v1-1-35ad2dddaf21@googlemail.com --- kernel/sysctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 9d3a666ffde1..dd337a63da41 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1171,7 +1171,7 @@ int proc_do_large_bitmap(const struct ctl_table *tabl= e, int dir, left--; } =20 - if (c =3D=3D '-') { + if (left && c =3D=3D '-') { err =3D proc_get_long(&p, &left, &val_b, &neg, tr_b, sizeof(tr_b), &c); --- base-commit: 80234b5ab240f52fa45d201e899e207b9265ef91 change-id: 20260312-fix-uninitialized-variable-in-proc_do_large_bitmap-30c6= ef4ac1c5 Best regards, --=20 buermarc