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97143b9d31
`snprintf()` is meant to protect against buffer overflows, but operating on the buffer using its return value, possibly by calling it again, can cause a buffer overflow, because it will return how many characters it would have written if it had enough space even when it did not. In a number of places, we repeatedly call snprintf() by successively incrementing a buffer offset and decrementing a buffer length, by its return value. This is a potentially unsafe usage of `snprintf()` whenever the buffer length is reached. CodeQL complained about this. To fix this, we introduce `kmem_scnprintf()`, which will return 0 when the buffer is zero or the number of written characters, minus 1 to exclude the NULL character, when the buffer was too small. In all other cases, it behaves like snprintf(). The name is inspired by the Linux and XNU kernels' `scnprintf()`. The implementation was written before I thought to look at `scnprintf()` and had a good name for it, but it turned out to have identical semantics to the Linux kernel version. That lead to the name, `kmem_scnprintf()`. CodeQL only catches this issue in loops, so repeated use of snprintf() outside of a loop was not caught. As a result, a thorough audit of the codebase was done to examine all instances of `snprintf()` usage for potential problems and a few were caught. Fixes for them are included in this patch. Unfortunately, ZED is one of the places where `snprintf()` is potentially used incorrectly. Since using `kmem_scnprintf()` in it would require changing how it is linked, we modify its usage to make it safe, no matter what buffer length is used. In addition, there was a bug in the use of the return value where the NULL format character was not being written by pwrite(). That has been fixed. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu> Closes #14098 |
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| .. | ||
| acl_impl.h | ||
| acl.h | ||
| atomic.h | ||
| byteorder.h | ||
| callb.h | ||
| ccompat.h | ||
| ccompile.h | ||
| cmn_err.h | ||
| condvar.h | ||
| cred.h | ||
| ctype.h | ||
| debug.h | ||
| dirent.h | ||
| disp.h | ||
| dkio.h | ||
| fcntl.h | ||
| file.h | ||
| freebsd_rwlock.h | ||
| idmap.h | ||
| inttypes.h | ||
| isa_defs.h | ||
| kmem_cache.h | ||
| kmem.h | ||
| kstat.h | ||
| list_impl.h | ||
| list.h | ||
| lock.h | ||
| misc.h | ||
| mod_os.h | ||
| mode.h | ||
| mount.h | ||
| mutex.h | ||
| param.h | ||
| policy.h | ||
| proc.h | ||
| processor.h | ||
| procfs_list.h | ||
| random.h | ||
| rwlock.h | ||
| sdt.h | ||
| sid.h | ||
| sig.h | ||
| simd_powerpc.h | ||
| simd_x86.h | ||
| simd.h | ||
| spl_condvar.h | ||
| string.h | ||
| sunddi.h | ||
| sysmacros.h | ||
| systeminfo.h | ||
| systm.h | ||
| taskq.h | ||
| thread.h | ||
| time.h | ||
| timer.h | ||
| trace_zfs.h | ||
| trace.h | ||
| types32.h | ||
| types.h | ||
| uio.h | ||
| uuid.h | ||
| vfs.h | ||
| vm.h | ||
| vmsystm.h | ||
| vnode_impl.h | ||
| vnode.h | ||
| wmsum.h | ||
| zmod.h | ||
| zone.h | ||