From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792543627; b=ddTXEire1IaSq3NtvR18iD0LvPqQzQ9ZyMi9P16k8aMgsxbwZVpCOcc9mNwzeqZrdR6l Ba5SMDS+i1i9f6Es9HUKq6iSRohGS3wZ2HtuE8hgEqjBS3MxorCkavDfWS4uTl2dIwdjA C1tJh0/xNqcSnzgfDzAJXBXZ2d5i9cZdnJEMWX+t6Rp6VZuwfx4/xvw68l15qFHSxzi51 65GS/FT52/VW0gnCGODYZCLFfsjZJVuYDCq+73BzkSdHFAhhurukNEEpelCsa/0cBMRuu YWsNFt3GXRDMIwYa25GGzwT4oIMS9lHHQaOmM/s8poSjbIuu/uCgVSJBrojPrUctHFA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792543627; h=Received:DKIM-Signature:Date:To:From:Message-Id:Subject; bh=+4J1ikdWRodL866L8ZB4HIPzbxbjVfCP68OwuDLd9b4=; b=SQyoTjJIjAcTfOU4TEWJwBONKZP+OTwKnhekFToKt/P72kRTFeyMpbIhvyS7JBfwiGeo egqLa3L2F9fIDRVOsEoEYTGWJ6jEdPT2I2USmLKFigk9rGGmB+al4dVuL0pkB0Nu2eV96 hFGa66I3yU9Iu0DMr2KbK8IDOSsD9N/fRmogfS5+KQ4d1VioW9UxoZGGqhUCI0rdWSV5F OlC6UNaIPq9aXVyM+F/4Y2B9HUhbSqZIbxPeEqj13AjeSJOv7bgFmnfZqpnPjfeLcW/X6 YZgjYR641xlk3JKY+/6X+2YJx9IHJ7jRLKLP4W0+TZVWFwws75Odw+Or91JZqRA/rbw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=qqDa1njb; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 57232606A31A for ; Wed, 21 Oct 2026 00:47:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=qqDa1njb Received: by smtp.kernel.org (Postfix) with ESMTPSA id C138D1F000C9; Wed, 21 Oct 2026 00:47:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1792543626; bh=+4J1ikdWRodL866L8ZB4HIPzbxbjVfCP68OwuDLd9b4=; h=Date:To:From:Subject; b=qqDa1njbkZe3Jb/X/idIDIrbjuJAeHiqQ8Uye35Zp0RHI9inkDG7hqHLBR55gJb7c OZ9/j6/mJfnIeDL1Ksxv5IxVDGqedRvhZH0vxkP9eRonl1vXeoIN9dVA+Q+d3T9/mq ZdAtDmYpEu4T6uTNtISDlyajruMd29aVWzZ1qvpE= Date: Tue, 20 Oct 2026 17:47:06 -0700 To: thnkslprpt@gmail.com,brads@mainlining.org,akpm@linux-foundation.org,linux-kernel@vger.kernel.org From: Andrew Morton Message-Id: Subject: [PATCH 1/2] profile: account for partial /proc/profile reads X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list From: Andrew Morton Subject: profile: account for partial /proc/profile reads Date: Tue, 20 Oct 2026 15:28:00 -0700 read_profile() returns -EFAULT without advancing the file position when a user copy faults, even if earlier header bytes or a prefix of the counters were successfully copied. A retry can therefore copy the same bytes again despite the previous read having delivered data. Return the number of successfully copied bytes and advance *ppos by that amount. Return -EFAULT only if the fault occurs before any bytes are copied. Preserve the four-byte sampling-step header, raw counter representation, and normal successful-read behavior. Avi Weiss's "profiling: fix sampling step on 64-bit big-endian systems" is unchanged. This patch changes only short-read and fault reporting, not the output format. Signed-off-by: Andrew Morton --- Tested the combined three-patch series on x86-64 QEMU/KVM with CONFIG_PROFILING=y, CONFIG_PROC_FS=y and profile=12. profile-read-test.c: PASS (0 failures). Covered header decoding, short and boundary reads, EOF, partial user-copy faults, return values and file-position accounting. The 64-bit big-endian fix was not runtime tested. There was no individual-patch or unpatched-versus-patched runtime comparison. kernel/profile.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/kernel/profile.c~profile-account-for-partial-proc-profile-reads +++ a/kernel/profile.c @@ -157,6 +157,7 @@ read_profile(struct file *file, char __u ssize_t read; char *pnt; unsigned int sample_step = (unsigned int)(1UL << prof_shift); + size_t not_copied; if (p >= (prof_len+1)*sizeof(unsigned int)) return 0; @@ -166,15 +167,21 @@ read_profile(struct file *file, char __u while (p < sizeof(unsigned int) && count > 0) { if (put_user(*((char *)(&sample_step)+p), buf)) - return -EFAULT; + goto out; buf++; p++; count--; read++; } - pnt = (char *)prof_buffer + p - sizeof(atomic_t); - if (copy_to_user(buf, (void *)pnt, count)) - return -EFAULT; - read += count; + if (count) { + pnt = (char *)prof_buffer + p - sizeof(atomic_t); + not_copied = copy_to_user(buf, pnt, count); + read += count - not_copied; + if (not_copied) + goto out; + } *ppos += read; return read; +out: + *ppos += read; + return read ? read : -EFAULT; } /* default is to not implement this call */ _