From bf5ed2ef5cdb7b47ce606e3d48ea6eb803b31503 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Tue, 11 Aug 2026 20:09:46 -0400 Subject: [PATCH] fs: don't block write during exec on pre-content watched files [ Upstream commit 0357ef03c94ef835bd44a0658b8edb672a9dbf51 ] Commit 2a010c412853 ("fs: don't block i_writecount during exec") removed the legacy behavior of getting ETXTBSY on attempt to open and executable file for write while it is being executed. This commit was reverted because an application that depends on this legacy behavior was broken by the change. We need to allow HSM writing into executable files while executed to fill their content on-the-fly. To that end, disable the ETXTBSY legacy behavior for files that are watched by pre-content events. This change is not expected to cause regressions with existing systems which do not have any pre-content event listeners. Signed-off-by: Amir Goldstein Acked-by: Christian Brauner Signed-off-by: Jan Kara Link: https://patch.msgid.link/20241128142532.465176-1-amir73il@gmail.com Stable-dep-of: db1856ea9196 ("binfmt_misc: restore write access when removing an entry") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/binfmt_elf.c | 4 ++-- fs/binfmt_elf_fdpic.c | 4 ++-- fs/exec.c | 6 +++--- include/linux/fs.h | 12 ++++++++++++ kernel/fork.c | 12 ++++++------ 5 files changed, 25 insertions(+), 13 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index e4348dd76658..0fbf5474b8fe 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1287,7 +1287,7 @@ out_free_interp: } reloc_func_desc = interp_load_addr; - allow_write_access(interpreter); + exe_file_allow_write_access(interpreter); fput(interpreter); kfree(interp_elf_ex); @@ -1396,7 +1396,7 @@ out_free_dentry: kfree(interp_elf_ex); kfree(interp_elf_phdata); out_free_file: - allow_write_access(interpreter); + exe_file_allow_write_access(interpreter); if (interpreter) fput(interpreter); out_free_ph: diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index d872ccb5f4b2..70b8a987de22 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -398,7 +398,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) goto error; } - allow_write_access(interpreter); + exe_file_allow_write_access(interpreter); fput(interpreter); interpreter = NULL; } @@ -471,7 +471,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm) error: if (interpreter) { - allow_write_access(interpreter); + exe_file_allow_write_access(interpreter); fput(interpreter); } kfree(interpreter_name); diff --git a/fs/exec.c b/fs/exec.c index 9d3e2eda9d55..359158943746 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -935,7 +935,7 @@ static struct file *do_open_execat(int fd, struct filename *name, int flags) path_noexec(&file->f_path)) goto exit; - err = deny_write_access(file); + err = exe_file_deny_write_access(file); if (err) goto exit; @@ -1521,7 +1521,7 @@ static void free_bprm(struct linux_binprm *bprm) abort_creds(bprm->cred); } if (bprm->file) { - allow_write_access(bprm->file); + exe_file_allow_write_access(bprm->file); fput(bprm->file); } if (bprm->executable) @@ -1824,7 +1824,7 @@ static int exec_binprm(struct linux_binprm *bprm) bprm->file = bprm->interpreter; bprm->interpreter = NULL; - allow_write_access(exec); + exe_file_allow_write_access(exec); if (unlikely(bprm->have_execfd)) { if (bprm->executable) { fput(exec); diff --git a/include/linux/fs.h b/include/linux/fs.h index e6b2e2749e37..12ea9af49a89 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2824,6 +2824,18 @@ static inline void allow_write_access(struct file *file) if (file) atomic_inc(&file_inode(file)->i_writecount); } + +static inline int exe_file_deny_write_access(struct file *exe_file) +{ + return deny_write_access(exe_file); +} +static inline void exe_file_allow_write_access(struct file *exe_file) +{ + if (unlikely(!exe_file)) + return; + allow_write_access(exe_file); +} + static inline bool inode_is_open_for_write(const struct inode *inode) { return atomic_read(&inode->i_writecount) > 0; diff --git a/kernel/fork.c b/kernel/fork.c index 36854aaec482..73e8a6b430a0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -640,8 +640,8 @@ static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm) * We depend on the oldmm having properly denied write access to the * exe_file already. */ - if (exe_file && deny_write_access(exe_file)) - pr_warn_once("deny_write_access() failed in %s\n", __func__); + if (exe_file && exe_file_deny_write_access(exe_file)) + pr_warn_once("exe_file_deny_write_access() failed in %s\n", __func__); } #ifdef CONFIG_MMU @@ -1431,13 +1431,13 @@ int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) * We expect the caller (i.e., sys_execve) to already denied * write access, so this is unlikely to fail. */ - if (unlikely(deny_write_access(new_exe_file))) + if (unlikely(exe_file_deny_write_access(new_exe_file))) return -EACCES; get_file(new_exe_file); } rcu_assign_pointer(mm->exe_file, new_exe_file); if (old_exe_file) { - allow_write_access(old_exe_file); + exe_file_allow_write_access(old_exe_file); fput(old_exe_file); } return 0; @@ -1476,7 +1476,7 @@ int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) return ret; } - ret = deny_write_access(new_exe_file); + ret = exe_file_deny_write_access(new_exe_file); if (ret) return -EACCES; get_file(new_exe_file); @@ -1488,7 +1488,7 @@ int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) mmap_write_unlock(mm); if (old_exe_file) { - allow_write_access(old_exe_file); + exe_file_allow_write_access(old_exe_file); fput(old_exe_file); } return 0;