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b=Q+4J0Pd6ng6ubEjGKldN+ZwnNlaXTHRBG4JDGidI/IFXx3AiPc5GYSSB8dqilObCI DeHusH9lngPlqGDv761pwm/nPtfB6CWlhryRuw+077asKZRErtQv6fvHr72V2kTk/v lTp5Rds+eFiZylc4Mm5T/eVoIyIZ6FvpDf/HPEq6cFC3j6XmOpsVvitO0Xh1aCcVyi dNY2OgZ5fNVud9Ry28m7d2TiJU99WLMgTPI1U4w6/yGfodxj0ugFp1XCfFTc9I3xbl R2ZPBJJcG5inqt1O082blA2cwCARQCitjSa1VN+rwp47B0vFqeEj0x+EPMoKVTHsZG 3dScYBrQpxFQA== From: Christian Brauner Date: Fri, 10 Jul 2026 11:33:03 +0200 Subject: [PATCH v3 02/24] binfmt_misc: use exe_file_deny_write_access() for the interpreter clone MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260710-work-binfmt_misc-locking-v3-2-a162f7cb58d6@kernel.org> References: <20260710-work-binfmt_misc-locking-v3-0-a162f7cb58d6@kernel.org> In-Reply-To: <20260710-work-binfmt_misc-locking-v3-0-a162f7cb58d6@kernel.org> To: linux-fsdevel@vger.kernel.org Cc: Alexander Viro , Christian Brauner , Jan Kara , linux-mm@kvack.org, Farid Zakaria , jannh@google.com, stable@vger.kernel.org X-Mailer: b4 0.16-dev-4217c X-Developer-Signature: v=1; a=openpgp-sha256; l=2087; i=brauner@kernel.org; h=from:subject:message-id; bh=AYPobXhR7tlhSW9eVD0N+FrhRjSI1w+57SYynhHowac=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWQF7InL7jz/42a2SStPxL6X2XHSW85+ePiljGFT9Txrg bv3P65N6ShlYRDjYpAVU2RxaDcJl1vOU7HZKFMDZg4rE8gQBi5OAZiIyS1GhrfvXG0CXqa2Pbya Yz0xyGbdMT9D3hi3XalnlC5MimI3sGdkuJ7Zb3wooV30yU21FsXU91d4//5jvvooLC1mWnLtg56 r7AA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C4E39160003 X-Stat-Signature: m9yf9beyxdaziubhthhstq7idhtpkdxu X-Rspam-User: X-HE-Tag: 1783676006-484026 X-HE-Meta: U2FsdGVkX19Sno02qi9y3GgtuQyCSLd9VY7hxsZbYaDuhO1xm1+aO6w6u0ohYlWphq0wiA+UCuIhX3Kd22kv9C64NzU1GZxwB0cnc5oIv5LHNbzBwoaaZRt8bwui0PknMLIpLq83Lk2Bubfc/DPK7/XxUHshUSJKxb+rpL5C3X4YZojXoTvEqAsjBSphhV0fPjD2On5OKIxsxK/wWasxMQUfKAlBzuSr3LvEIfwIBfACAcfK1d9tevctGivRi4Pil3y4e150yuKLOkAZPhBu9VrjoGO3+buFU34eJSEVn/rU7eT68q+FxMvgg0+XVGnkBzsEoxjh5kK6wBnJt95OONiSCBa86C89/+eJ6wCM1jPBZskBh9N5+6EMpD3VUDmYF6Gk4/CTjWqhFJv/w6uF7/xPFM89OwKrsby7mPjBhuN8ABs1yw/Guhk7ezkRrrjF5MmPxpMjdH/vxu4PMFuHPcr155hQkTdi5dSdetI+Ru0SPEpx35gYr+KdQAfL9qUcizrkw19o/3EQSG/we3nde4pEgf4oMCQFg8sKgVrGVSZvybi0rDdewrtUvPNMvWptzd1A6V4ialAiIbfVDRd+TiH9HOdb4Ze0+QyzIBcOX0fYE81SSYXXFva+eQT/sNANXyKdfpBplSj3vsWpwnrWm4H+aIParxQ97x3zbU3KRI/tbic8aFQJQE4xOsH5x4RmXVvty7Pog64OFkH07s3XRSh2LHeW+7K4ym2rVXaTILpllxILuG01olWcZIW7EHdiLBbZhhpiaaJM8cCRMtwIrsNGQwXX34r8ZRs39DKHmShggVMzGTjUz1A0apZjj8GDtlnLzVMkazU/p1Sn6QKy7x0oZJ+LM/hWc+t+w4+qvLZU4mVdsv6aMCNWseqD9yJTEEUzR/+dwjQ02wiHaJLaOEIHtf7NfBRcyEEN3g/Eh2wb5X3VD+3RT9rBN8ZdxT7qNSWCo7+RcUM7hPSkvvY AGLXcEEQ j37pRqYfZM61OEyj0qM5IStrdQhgSuHcvCt6pyXRBwZdaXg7NozPqnHg16afK+PMpTjp4eJrClNcbrO6MfjraxO+vGB0kjlwio+8+5R8bJwS9wmqrpxftJgkLkAB7Gor7yuU6EdCymgRaeBBOymvEF7e05WBLghCwZuDgyCGReAj1Hjh9JRfb0kuD9rgUaWoZBNxjfM+JZGoxFS+fK6msuYSzedq1u2HRuZh3lrObRHY2GoahLuUxjqHTERcsgceuXUTATWIRPEHLj/nMHFPGyRymHF3qRTHg+r+0RVYy8rHjJfIFUnO+K8bs9Gn2964MnyD99qsEFrK2/0K5VHdDXuiRPnaG1j7iV3ehJ3+2XSEUMxbigy1wPzaGjOlB3NdJyWBqmKFljbih9jk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: For MISC_FMT_OPEN_FILE entries load_misc_binary() clones the registered interpreter file and denies write access to the clone via plain deny_write_access(). The clone is installed as bprm->interpreter and later released by the exec machinery through exe_file_allow_write_access() which skips the i_writecount increment for files with FMODE_FSNOTIFY_HSM set. The deny and allow side can therefore come to different conclusions when pre-content watches are in play: if a pre-content watch is added to the interpreter after registration every subsequent exec through that entry takes a write denial on the clone that is never paired with a write allowance, driving the interpreter inode's i_writecount further down with each exec and leaving the interpreter unwritable even after the entry and all its users are gone. Take the write denial via exe_file_deny_write_access() so both sides of the pairing base their decision on the same file mode, and propagate failure instead of silently ignoring it: an interpreter that is concurrently open for writing now fails the exec with ETXTBSY, exactly like an interpreter freshly opened via open_exec() would. Fixes: 0357ef03c94e ("fs: don't block write during exec on pre-content watched files") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- fs/binfmt_misc.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index de50a7468b07..24142859658c 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -252,8 +252,14 @@ static int load_misc_binary(struct linux_binprm *bprm) if (fmt->flags & MISC_FMT_OPEN_FILE) { interp_file = file_clone_open(fmt->interp_file); - if (!IS_ERR(interp_file)) - deny_write_access(interp_file); + if (!IS_ERR(interp_file)) { + int err = exe_file_deny_write_access(interp_file); + + if (err) { + fput(interp_file); + interp_file = ERR_PTR(err); + } + } } else { interp_file = open_exec(fmt->interpreter); } -- 2.53.0