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Tue, 31 Mar 2026 11:21:49 -0700 (PDT) MIME-Version: 1.0 References: <20260331175456.4065874-1-luca.boccassi@gmail.com> In-Reply-To: <20260331175456.4065874-1-luca.boccassi@gmail.com> From: Pasha Tatashin Date: Tue, 31 Mar 2026 14:21:12 -0400 X-Gm-Features: AQROBzCTHvb05M0vcsTVPES6Ynk7b97-HrtYc5Ey0Occ_WM5chA1DLPefIFWYrc Message-ID: Subject: Re: [PATCH] liveupdate: truncate getfile name to NAME_MAX To: luca.boccassi@gmail.com Cc: kexec@lists.infradead.org, linux-mm@kvack.org, graf@amazon.com, rppt@kernel.org, pratyush@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 34F364000D X-Stat-Signature: 6xt7uqobzjogyfhid4mwmxccaij8eifz X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1774981310-968523 X-HE-Meta: U2FsdGVkX18F5zA3IPzYDXivPNs5aPXmK/Lu8psdhvMgj2YlazPSFxu4Mw4YT0BmtNG1EqsFenzBM+WcQS+0+y3zb3KnY1/9HB3KGFzrDmdCC2AhbbPNSYjZTnz0+O6t0vsKW/09Gl49CaMVcFlomE0H2jnftHdR93ZctifE1YF2HiyrPzifWTTJKwRWZkTsKfA5W+6CU3oSveyx+LBaLFFvYDaWoMNZNlydmNoSjZzsODDdKNdx3kUUBknP5hhbNtnxXuSsNL0d2tu0Umh2iFJ/BNxWZRnCi796A+VplXTv3X39ij0pC51JDPGUDLZMtD5rV1op1GnjL2tX/hl/lzOQbfntZgCLj7lOaZaFx12phW2TjeCdR+hW5ioLICj82pZYki29dKQLYA9NU/ZzC9L2AqSmjAckee72D96wXxN0JQUR7ODO8f1NrLAISNEZR4SoOj9PSNcQP4qPsCuiZxtYyxJmKXLp8twRNdoiYhRbpqsj2/G8m9Xucw4EeBmn4jPKePqX4U0eF9DTBl1ftSRGmoXrjvpZONl5uH80kPrEqVvH1rAE27YqoaKfPuoDlArAhr+VR46fKH/Ci3bfOHhnfrLkFl08afq+/b3H4KE3/8Xtril55IJO1DXObpCNdksD5n62s+8BLnAidcto2Jw76/e5rlG0wYkpoBObPApRQK1lKrI1/hRd+eq7vI9nNatBkvmin3odm8nDXxeYSz3rnm4BnrAyWkX4+lmKZvrNnsS0+WMhOgPPskHKvsHZqpO/Ac+bORdyJp6KaUP9UyroQJNCzsnyMfZ+OXW9cB/4tY3A2iA5T5uT3TyZvqhjNSVLhnpbVIDCu3DEgoI9jYdyAY4L9MiNS7TR7bCjthDJwac1pJLbGLN2XBDGOsSvR+ehZimCDBFZSkHebNTIpEmRMi2bJrfHpoqFLG3haqdIHDq+PpwQaS/B+QW1XXE6r9ovO/OjX+7B2s6ivbH yWE8OGCG 9wwRmBZuEGPr/jbUvmzM62WGMYX0xaWQNp4kq2wP/E/Cfs4vHp/ZwRwSpptZ4ceb8GM5Xd634+MSYI6uaEP26mhDzw6dlTaaqEgjdT1jS6HQyiEL2AatZ8RpNy6LgpZ4SkhDvzHtaq62DqvidniEmdQF02m4F44m2tWXJ6Pp1IxqY4GdstNCwb2JT9JSq7ffKIU72U4jOPEvAQ36UKD9m/z7I1YIKeYlJY+qoym81Qu0026UPSmCKu8HGzUopzEGuVFCd2e278ySHUNhE688s+cDjge8CPhrF+J5XF6dc/+46Rm/i2pnDnR/BH71UbEwbFY2W1QYW0y+AM/EksZ4YsOei06xl8Qy5VSDKz5XnzQ7syr7AWLYwROE1lzVtcy63pPyWjouKK57Y+gvWp9SHWgDGLHfYa70Y2nom65T5LKQZBCqfK7DHjOhrdPaezWr4KJyL1u7HoksFkfA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 31, 2026 at 1:55=E2=80=AFPM wrote: > > From: Luca Boccassi > > dynamic_dname() harcodes its limit to NAME_MAX bytes, which includes a > NUL terminator and a 'anon_inode:' prefix. If the name passed on goes > above the limit it results in userspace getting a ENAMETOOLONG error. > > Truncate the name to NAME_MAX - 12 - 1 characters to ensure this never > fails (accounting for prefix and NUL). > > Fixes: 0153094d03df ("liveupdate: luo_session: add sessions support") > > Signed-off-by: Luca Boccassi > --- > Builds on top of this just sent by Aleksa: > > https://lore.kernel.org/linux-fsdevel/20260401-dynamic-dname-name_max-v1-= 1-8ca20ab2642e@amutable.com/ > > kernel/liveupdate/luo_session.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_sess= ion.c > index 7836772956406..4a40c7fdfb44f 100644 > --- a/kernel/liveupdate/luo_session.c > +++ b/kernel/liveupdate/luo_session.c > @@ -366,11 +366,14 @@ static const struct file_operations luo_session_fop= s =3D { > /* Create a "struct file" for session */ > static int luo_session_getfile(struct luo_session *session, struct file = **filep) > { > - char name_buf[128]; > + char name_buf[NAME_MAX]; > struct file *file; > > lockdep_assert_held(&session->mutex); > - snprintf(name_buf, sizeof(name_buf), "[luo_session] %s", session-= >name); > + /* dynamic_dname() rejects names above NAME_MAX bytes, including = NUL terminator > + * and a 'anon_inode:' prefix. Truncate to NAME_MAX - 12 - 1 to a= void > + * ENAMETOOLONG. */ > + snprintf(name_buf, NAME_MAX - 12 - 1, "[luo_session] %s", session= ->name); I am confused by this change, the maximum session name length is: 64, as defined in: include/uapi/linux/liveupdate.h /* The maximum length of session name including null termination */ #define LIVEUPDATE_SESSION_NAME_LENGTH 64 So, 128 should be enough to include: "[luo_session] %s", session->name Or am I missing something? Pasha